Date post: | 31-Dec-2015 |
Category: |
Documents |
Upload: | sabina-dean |
View: | 231 times |
Download: | 0 times |
1.0 Atomic structure
Lister p 4 - 20
AQA AS Specification
Lessons Topics
1-2 Fundamental particles• be able to describe the properties of protons, neutrons and electrons in terms of relative charge and relative mass
3 Electron arrangement• know that early models of atomic structure predicted that atoms and ions with noble gas electron-arrangements should be stable
4-7 Mass number and isotopes• be able to recall the meaning of mass number (A) and atomic(proton) number (Z)• be able to explain the existence of isotopes• understand the principles of a simple mass spec,limited to ionisation, acceleration, deflection and detection, and its use for identifying elements and RMM
8-11 Electron arrangement• know the electron configurations of atoms and ions up to Z = 36 in terms of levels and sub-levels (orbitals) s, p and d• know the meaning of the term ionisation energy.• understand how ionisation energies in Period 3 (Na – Ar) and inGroup 2 (Be – Ba) give evidence for electron arrangement in sub-levels and in levels
The Atom
The atom consists of two parts:
1. The nucleus which contains:
2. Orbiting electrons.
protonsneutrons
Draw a model of an atom and label the main parts
Structure of an atom
• An atom consists of a central positively charged nucleus containing protons and neutrons (nucleons)
• Diameter approx. 10-15 m (1 femtometre)
• Electrons surround the nucleus
• Atomic diameter approx. 10-10 m roughly 100 000 x nucleus diameter
nucleus diameter ~ 10 – 15 m
atomic diameter ~ 10 – 10 m
If a helium atom was the size of a full stop, then the average gerbil would be the size of the
Earth.
If a helium atom was the size of a full stop, then the average gerbil would be the size of the
Earth.
Atoms: How small?
Now let’s pretend that the helium atom on the right is the size of the Earth.
What’s wrong with this simple picture?
Atoms: very small
The helium atom is not in the right proportions. The three subatomic particles are wrongly enormous in comparison to
the atom’s radius.
The helium atom is not in the right proportions. The three subatomic particles are wrongly enormous in comparison to
the atom’s radius.
How big is a nucleus?
Most of the atom is empty space!
If you imagine an atom being the size of Wembley stadium, the nucleus would be about the size of a
football on the centre spot.
The electrons would be two peas flying around the whole stadium. The rest of it: emptiness.
If you imagine an atom being the size of Wembley stadium, the nucleus would be about the size of a
football on the centre spot.
The electrons would be two peas flying around the whole stadium. The rest of it: emptiness.
Properties of subatomic particles
Property Proton, p Neutron, nElectron,
e-
Mass/ kg 1.673 x 10-
27
1.675 x 10-
27
0.911 x 10-
31
Charge/C +1.602 x10-19 0
-1.602 x 10-
19
Position In the nucleus
In the nucleus
Around the nucleus
Subatomic
particle
Relative charge
Relative mass
Common depictio
n
Proton +1 1
Neutron 0 1
Electron -1 1 10-5
+
-
Subatomic particles in more detail
Subatomic
particle
Relative charge
Relative mass
Common depictio
n
Proton +1 1
Neutron 0 1
Electron -1 1 10-5
+
-
Subatomic particles in more detail
1.2 Electron arrangement• How are electrons arranged in
atoms?They are arranged in shellsThey are arranged in shells
How do we know how many electrons are in each shell?
The shells are numbered outward from the nucleus.
The maximum number of electrons found in each shell can be calculated from 2n2 where n is the shell number.
The shells are numbered outward from the nucleus.
The maximum number of electrons found in each shell can be calculated from 2n2 where n is the shell number.
The shorthand form for, eg, Nitrogen, is 2,5The shorthand form for, eg, Nitrogen, is 2,5
Shell Number Maximum number of electrons
1 2 x 12 = 2 x 1 = 2
2 2 x 22 = 2 x 4 = 8
3 2 x 32 = 2 x 9 = 18
4 2 x 42 = 2 x 16 = 32
5 2 x 52 = 2 x 25 = 50
Task
Complete the following table:
Shell Number Maximum number of electrons
1
2
3
4
5
Now complete worksheet 1.1
1.3 Mass number, atomic number and isotopesHow can we describe an atom in terms of it’s subatomic structure?
What information do we need to know?
The number of protons is called the Atomic number .
What is significant about the number of protons in the nucleus?
The number of protonsThe number of neutronsThe number of electrons
The number of protonsThe number of neutronsThe number of electrons
It tells us what the element is and how many electrons are present in the neutral atom
It tells us what the element is and how many electrons are present in the neutral atom
The number of nucelons is called the Mass number .
What information can we get from this?
We can find out the number of neutronsWe can find out the number of neutrons
Li7
3
No. of protons + neutronsLithium
Number of protons
Number of electrons=
Atomic number does not always equal the number of neutrons.
Atomic number does not always equal the number of neutrons.
Lithium
Electrons
3
Protons 3
Neutrons
4
Mass number
(No. of protons)
Atomic number or proton number
LithiumNumber of
protonsNumber of electrons=
Lithium
Electrons
3
Protons 3
Neutrons
4
This is because the atom is neutral. The charges balance out
-3 charge
+3 charge
But atoms can gain and lose electrons (they become ions). This changes the overall charge on the atom.
But atoms can gain and lose electrons (they become ions). This changes the overall charge on the atom.
No charge
The number of protons “defines” an element – nothing else!The number of protons “defines” an element – nothing else!
Atomic number does not always equal the number of neutrons. This can change, even in atoms of the same element. These are called isotopes.
Atomic number does not always equal the number of neutrons. This can change, even in atoms of the same element. These are called isotopes.
7-Lithium (7Li)
Electrons 3
Protons 3
Neutrons 4
Some isotopes of lithium:
4Li 4-Lithium 3 protons,1 neutron
6Li 6-Lithium 3 protons,3 neutrons
10Li 10-Lithium 3 protons,7 neutrons
11Li 11-Lithium 3 protons,8 neutrons
Lithium: always 3 protons!
Isotopes
Complete:
Atom P n e-
Na
Rh
phosphorus
The last of the halogens
Xe
The only liquid non-metal
Li+
F-
Carbon-14 (14C)
A helium atom
He4
2
2 protons2 electrons2 neutrons
Answers
Atom P N ENa 11 12 11
Rh 45 58 45
phosphorus 15 16 15
The last of the halogens 85 125 85
Xe 54 77 54
The only liquid non-metal 35 45 35
Li+ 3 4 2
F- 9 10 10
Carbon-14 (14C) 6 8 6
Chemical properties of isotopes
Would you expect the isotopes of lithium to have the same chemical properties?
What is the Mass number, Z, of Chlorine?
Yes – chemistry is about the movement of electronsYes – chemistry is about the movement of electrons
How can you get a fraction of a nucleon?
35.535.5
The relative abundance of two chlorine isotopes is similar, hence the mass number on the PT is an average number determined by the abundances of the isotopes
The relative abundance of two chlorine isotopes is similar, hence the mass number on the PT is an average number determined by the abundances of the isotopes
1.4 Mass spectrometry
What does a mass spectrometer do?
It ionizes atoms and then sends them through an em field where they become deflected on the basis of their mass and charge
It ionizes atoms and then sends them through an em field where they become deflected on the basis of their mass and charge
Why is it important that the instrument is under vacuum?
To prevent collisions of the ions with gas moleculesTo prevent collisions of the ions with gas molecules
How are samples put into the machine?
Volatile liquids and gases can be injected directly, solids must be vapourised.
Volatile liquids and gases can be injected directly, solids must be vapourised.
http://www.youtube.com/watch?v=J-wao0O0_qM&feature=related
Mass Spectrometer
A
B
C
D
E
F
G
Mass Spectrometry - summary
Sample vapourised
Sample ionised positive ions
+ve ions in beam accelerated by electric field
Vacuum pump to keep whole apparatus at v. low pressure
+ve ions subjected to variable magnetic field
+ve ions separated according to mass: charge ratio
+ve ions detected and measured mass spectrum
LOWER m:z ratio
HIGHER m:z ratio
State what happens at each of the locations A-G
Calculating RAM of atoms
Calculate the relative atomic mass of boron.
The tallest “stick” is often (but not always) set at 100
The tallest “stick” is often (but not always) set at 100
boron-10 23 boron-11 100
(100 x 11) + (23 x 10)/123 = 10.8
boron-10 23 boron-11 100
(100 x 11) + (23 x 10)/123 = 10.8
http://www.chem.uoa.gr/applets/AppletMS/Appl_Ms2.html
QuestionHow many isotopes does this element have? What element is it?
Calculate the RAM
51.5
11.2
17.1 17.4
2.8
Answer
51.5
11.2
17.1 17.4
2.8
Step 1: Find the total mass of these 100 typical atoms:(51.5 x 90) + (11.2 x 91) + (17.1 x 92) + (17.4 x 94) + (2.8 x 96) = 9131.8
Step 1: Find the total mass of these 100 typical atoms:(51.5 x 90) + (11.2 x 91) + (17.1 x 92) + (17.4 x 94) + (2.8 x 96) = 9131.8
Step 2: find the average mass of these 100 atoms :9131.8 / 100 = 91.3 (to 3 sig fig).Step 2: find the average mass of these 100 atoms :9131.8 / 100 = 91.3 (to 3 sig fig).
91.3 is the relative atomic mass of zirconium.91.3 is the relative atomic mass of zirconium.
The mass spectrum of uranium has 3 peaks: at 234 m/z, 235 m/z and 238 m/z. The abundance of the isotopes is 0.006%, 0.72% and 99.2% respectively. What is the average relative atomic mass of uranium?
240
237.0
237.8
238
Question
Question
Chlorine has two isotopes, 35Cl and 37Cl, in the approximate ratio of 3 atoms of 35Cl to 1 atom of 37Cl. Draw the stick diagram for Chlorine
Question
Chlorine has two isotopes, 35Cl and 37Cl, in the approximate ratio of 3 atoms of 35Cl to 1 atom of 37Cl. Draw the stick diagram for Chlorine
Wrong!Why?Wrong!Why?
The problem is that chlorine consists of molecules, not individual atoms.
When chlorine is passed into the ionisation chamber, an electron is knocked off the molecule to give a molecular ion, Cl2+. Doubly charges ions can also form.
These ions aren’t very stable, and some will fall apart to give a chlorine atom and a Cl+ ion. The term for this is fragmentation
The problem is that chlorine consists of molecules, not individual atoms.
When chlorine is passed into the ionisation chamber, an electron is knocked off the molecule to give a molecular ion, Cl2+. Doubly charges ions can also form.
These ions aren’t very stable, and some will fall apart to give a chlorine atom and a Cl+ ion. The term for this is fragmentation
Chlorine MS
Cl2+ Cl + Cl+ Cl2+ Cl + Cl+
What can molecular chlorine ions (Cl2+ ) fragment into?
What happens to the Cl atom? If it doesn’t acquire a charge in the ionization chamber then it gets “lost” in the MS
If it doesn’t acquire a charge in the ionization chamber then it gets “lost” in the MS
What are the possible combinations of chlorine-35 and chlorine-37 atoms in a Cl2+ ion?
Both atoms could be 35Cl, both atoms could be 37Cl, or you could have one of each sort.
Masses of the Cl2+ ion: 35 + 35 = 7035 + 37 = 7237 + 37 = 74
Both atoms could be 35Cl, both atoms could be 37Cl, or you could have one of each sort.
Masses of the Cl2+ ion: 35 + 35 = 7035 + 37 = 7237 + 37 = 74
What would the MS look like?
Chlorine MS …
Why is there no scale on the y-axis?
Because you cannot predict how the molecules will ionize and fragment
Because you cannot predict how the molecules will ionize and fragment
1.5 Electron configurations
Why is the periodic table broken up into sections? What links each of these sections?
The distribution of electrons within the shells is, in most cases, more complicated than simple spheres. The regions within the PT closely follow the patterns of these distributions – or probabilities of electron density
The distribution of electrons within the shells is, in most cases, more complicated than simple spheres. The regions within the PT closely follow the patterns of these distributions – or probabilities of electron density
http://www.yellowtang.org/images/electrons_atoms_pos_c_la_784.jpgThe shells represent energy
levels in atoms. Electrons can move between these levels, gaining or losing energy in the process.
The shells represent energy levels in atoms. Electrons can move between these levels, gaining or losing energy in the process.
Sublevels
Each energy level is divided into one or more sublevels. These sublevels have energies that differ slightly from that of the shell energy.
Each energy level is divided into one or more sublevels. These sublevels have energies that differ slightly from that of the shell energy.
How many types of sublevel are there?
(hint – think about he number of regions in the PT)
There are 4: s.p.d.fThe “s-block” comprises Groups 1 and 2The “p- block” comprises Groups 3 - 8
There are 4: s.p.d.fThe “s-block” comprises Groups 1 and 2The “p- block” comprises Groups 3 - 8
How many electrons can an s sublevel have in it?
How many electrons can a p sublevel have in it?
Edps
3
2
1
What is the significance of the order of the subshells?
Atomic orbitals
Sublevels aren’t all the same.
The s-sublevel has the lowest energy and so is filled first. It can hold a maximum of two electrons.
The s orbital is spherical and represents the probability of finding the electrons within its boundary
Sublevels aren’t all the same.
The s-sublevel has the lowest energy and so is filled first. It can hold a maximum of two electrons.
The s orbital is spherical and represents the probability of finding the electrons within its boundary
The p-, d- and f- sublevels are degenerate, ie further broken down into more sublevels of almost equivalent energy.
The p-, d- and f- sublevels are degenerate, ie further broken down into more sublevels of almost equivalent energy.
If a p-orbital can hold 6 electrons in total, how many degenerate orbitals are there?
Orbital shapes
Spin
Electron s are either spin up, or spin down – ie clockwise or anticlockwise. (corresponding to a spin quantum number of +1/2 and -1/2)
Electron s are either spin up, or spin down – ie clockwise or anticlockwise. (corresponding to a spin quantum number of +1/2 and -1/2)
Degenerate orbitals of the same energy fill up first. Parallel spins go in first followed by antiparallel spin.
Degenerate orbitals of the same energy fill up first. Parallel spins go in first followed by antiparallel spin.
1s 2s 2px 2py 2pz
Nomenclature: the number of electrons in a particular orbital is denoted by superscript. e.g. 1s2 2s2 3p2
Nomenclature: the number of electrons in a particular orbital is denoted by superscript. e.g. 1s2 2s2 3p2
Electrons have a property called “spin”. This determines the way in which the degenerate levels are populated.
Electrons have a property called “spin”. This determines the way in which the degenerate levels are populated.
Aufbau
Orbitals do not always fill up in the way expectedOrbitals do not always fill up in the way expected
This is due to overlap in the energies of the sublevels
This is due to overlap in the energies of the sublevels
Look at the energy level diagram for Silicon. Which orbitals have energy levels which overlap?
The 4s orbital has an energy between that of the 3p and 3d orbitals. This means that the 4s orbital fills before the 3d orbital.
The 4s orbital has an energy between that of the 3p and 3d orbitals. This means that the 4s orbital fills before the 3d orbital.
Filling orbitals
Electrons enter the lowest energy orbital available (Aufbau principle)Electrons enter the lowest energy orbital available (Aufbau principle)
In the periodic table, the transition elements make up the “d-block”.
The first row in the d-block contains the 3d elements. These follow from the 4s elements, Potassium and Calcium.
In the periodic table, the transition elements make up the “d-block”.
The first row in the d-block contains the 3d elements. These follow from the 4s elements, Potassium and Calcium.
Electrons prefer to occupy orbitals on their own, and only pair up when no empty orbitals of the same energy are available (Hund's Rule)
Electrons prefer to occupy orbitals on their own, and only pair up when no empty orbitals of the same energy are available (Hund's Rule)
Complete worksheet 1.5
THE BOHR ATOMTHE BOHR ATOM
Ideas about the structure of the atom have changed over the years. The Bohr theory
thought of it as a small nucleus of protons and neutrons surrounded by circulating electrons.
Each shell or energy level could hold a maximum number of electrons.
The energy of levels became greater as they got further from the nucleus and electrons filled
energy levels in order.
The theory couldn’t explain certain aspects of chemistry.
Maximum electrons per shell
1st shell 2
2nd shell 8
3rd shell 18
4th shell 32
5th shell 50
1
2
3
4
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
SLEVELS AND SUB-LEVELSLEVELS AND SUB-LEVELS
PRINCIPAL ENERGY LEVELS
During studies of the spectrum of hydrogen it was shown that the energy
levels were not equally spaced. The energy gap between successive levels got increasingly smaller as the levels
got further from the nucleus. The importance of this is discussed later.
1
2
3
4
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
SLEVELS AND SUB-LEVELSLEVELS AND SUB-LEVELS
During studies of the spectrum of hydrogen it was shown that the energy
levels were not equally spaced. The energy gap between successive levels got increasingly smaller as the levels
got further from the nucleus. The importance of this is discussed later.
A study of Ionisation Energies and the periodic properties of elements suggested that the main energy levels were split
into sub levels.
Level 1 was split into 1 sub level
Level 2 was split into 2 sub levels
Level 3 was split into 3 sub levels
Level 4 was split into 4 sub levels
SUB LEVELS
CONTENTSCONTENTS
PRINCIPAL ENERGY LEVELS
RULES AND PRINCIPLESRULES AND PRINCIPLES
HEISENBERG’S UNCERTAINTY PRINCIPLE
“You cannot determine the position and momentum of an electron at the same time.”
This means that you cannot say exactly where an electron is. It put paid to the idea of electrons orbiting the nucleus in rings and introduced the idea of orbitals.
THE AUFBAU PRINCIPLE
“Electrons enter the lowest available energy level.”
PAULI’S EXCLUSION PRINCIPLE
“No two electrons can have the same four quantum numbers.”
Two electrons can go in each orbital, providing they are of opposite spin.
HUND’S RULE OF MAXIMUM MULTIPLICITY
“When in orbitals of equal energy, electrons will try to remain unpaired.”
Placing two electrons in one orbital means that, as they are both negatively charged, there will be some electrostatic repulsion between them. Placing each electron in a
separate orbital reduces the repulsion and the system is more stable. It can be described as the “SITTING ON A BUS RULE”!
ORBITALSORBITALS
An orbital is... a region in space where one is likely to find an electron.
Orbitals can hold up to two electrons as long as they have opposite spin; this is known as PAULI’S EXCLUSION PRINCIPAL.
Orbitals have different shapes...
ORBITALSORBITALS
An orbital is... a region in space where one is likely to find an electron. a region in space where one is likely to find an electron.
Orbitals can hold up to two electrons as long as they have opposite spin; this is known as PAULI’S EXCLUSION PRINCIPAL.
Orbitals have different shapes...
ORBITAL SHAPE OCCURRENCE
s spherical one in every principal level
p dumb-bell three in levels from 2 upwards
d various five in levels from 3 upwards
f various seven in levels from 4 upwards
ORBITALSORBITALS
An orbital is... a region in space where one is likely to find an electron. a region in space where one is likely to find an electron.
Orbitals can hold up to two electrons as long as they have opposite spin; this is known as PAULI’S EXCLUSION PRINCIPAL.
Orbitals have different shapes...
ORBITAL SHAPE OCCURRENCE
s spherical one in every principal level
p dumb-bell three in levels from 2 upwards
d various five in levels from 3 upwards
f various seven in levels from 4 upwards
An orbital is a 3-dimensional statistical shape showing where one is most likely to find an electron. Because, according to Heisenberg, you cannot say exactly where
an electron is you are only able to say where it might be found.
DO NOT CONFUSE AN ORBITAL WITH AN ORBIT
SHAPES OF ORBITALSSHAPES OF ORBITALS
s orbitals
• spherical
• one occurs in every principal energy level
SHAPES OF ORBITALSSHAPES OF ORBITALS
p orbitals
• dumb-bell shaped
• three occur in energy levels except the first
SHAPES OF ORBITALSSHAPES OF ORBITALS
d orbitals
• various shapes
• five occur in energy levels except the first and second
Orbitals are not filled in numerical order because the principal energy levels get closer together as you get further from the nucleus. This results in overlap of sub levels. The first example occurs when the 4s orbital is filled before the 3d orbitals.
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
S
1 1s
22s
2p
4s
33s3p3d
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
ORDER OF FILLING ORBITALSORDER OF FILLING ORBITALS
Orbitals are not filled in numerical order because the principal energy levels get closer together as you get further from the nucleus. This results in overlap of sub levels. The first example occurs when the 4s orbital is filled before the 3d orbitals.
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
S
1 1s
22s
2p
4s
33s3p3d
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
1 1s
22s
2p
3d
33s3p4s
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
ORDER OF FILLING ORBITALSORDER OF FILLING ORBITALS
Orbitals are not filled in numerical order because the principal energy levels get closer together as you get further from the nucleus. This results in overlap of sub levels. The first example occurs when the 4s orbital is filled before the 3d orbitals.
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
S
1 1s
22s
2p
4s
33s3p3d
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
1 1s
22s
2p
3d
33s3p4s
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
ORDER OF FILLING ORBITALSORDER OF FILLING ORBITALS
THE FILLING ORDER
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
HOW TO HOW TO REMEMBER ..REMEMBER ....
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
S
This states that…
“ELECTRONS ENTER THE LOWEST AVAILABLE
ENERGY LEVEL”
THE ‘AUFBAU’ PRINCIPALTHE ‘AUFBAU’ PRINCIPAL
The following sequence will show the ‘building up’ of the electronic structures of the
first 36 elements in the periodic table.
Electrons are shown as half headed arrows and can spin
in one of two directions
or
s orbitals
p orbitals
d orbitals
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
S
HYDROGEN
1s1
THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
Hydrogen atoms have one electron. This goes into a
vacant orbital in the lowest available energy level.
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
S
HELIUM
1s2
THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
Every orbital can contain 2 electrons, provided the
electrons are spinning in opposite directions. This is
based on...
PAULI’S EXCLUSION PRINCIPLE
The two electrons in a helium atom can both go in
the 1s orbital.
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
LITHIUM
1s orbitals can hold a maximum of two electrons so the third electron in a
lithium atom must go into the next available orbital of higher energy. This will be further from the nucleus in
the second principal energy level.
The second principal level has two types of orbital (s
and p). An s orbital is lower in energy than a p.
1s2 2s1
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
BERYLLIUM
Beryllium atoms have four electrons so the fourth
electron pairs up in the 2s orbital. The 2s sub level is
now full.
1s2 2s2
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
BORON
As the 2s sub level is now full, the fifth electron goes
into one of the three p orbitals in the 2p sub level. The 2p orbitals are slightly higher in energy than the
2s orbital.
1s2 2s2 2p1
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
CARBON
The next electron in doesn’t pair up with the one already there. This
would give rise to repulsion between the
similarly charged species. Instead, it goes into
another p orbital which means less repulsion, lower energy and more
stability.
1s2 2s2 2p2
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
NITROGEN
Following Hund’s Rule, the next electron will not
pair up so goes into a vacant p orbital. All three
electrons are now unpaired. This gives less repulsion, lower energy
and therefore more stability.
1s2 2s2 2p3
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
OXYGEN
With all three orbitals half-filled, the eighth electron in an oxygen atom must now
pair up with one of the electrons already there.
1s2 2s2 2p4
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
FLUORINE
The electrons continue to pair up with those in the
half-filled orbitals.
1s2 2s2 2p5
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
NEON
The electrons continue to pair up with those in the
half-filled orbitals. The 2p orbitals are now
completely filled and so is the second principal
energy level.
In the older system of describing electronic
configurations, this would have been written as 2,8.
1s2 2s2 2p6
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
SODIUM - ARGON
With the second principal energy level full, the next electrons must go into the
next highest level. The third principal energy level
contains three types of orbital; s, p and d.
The 3s and 3p orbitals are filled in exactly the same
way as those in the 2s and 2p sub levels.
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
SODIUM - ARGON
Na 1s2 2s2 2p6 3s1
Mg 1s2 2s2 2p6 3s2
Al 1s2 2s2 2p6 3s2 3p1
Si 1s2 2s2 2p6 3s2 3p2
P 1s2 2s2 2p6 3s2 3p3
S 1s2 2s2 2p6 3s2 3p4
Cl 1s2 2s2 2p6 3s2 3p5
Ar 1s2 2s2 2p6 3s2 3p6
Remember that the 3p configurations follow Hund’s
Rule with the electrons remaining unpaired to give
more stability.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
POTASSIUM
In numerical terms one would expect the 3d
orbitals to be filled next.
However, because the principal energy levels get closer together as you go further from the nucleus coupled with the splitting into sub energy levels, the 4s orbital is of a LOWER
ENERGY than the 3d orbitals so gets filled first.
1s2 2s2 2p6 3s2 3p6 4s1
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
CALCIUM
As expected, the next electron pairs up to
complete a filled 4s orbital.
This explanation, using sub levels fits in with the
position of potassium and calcium in the Periodic
Table. All elements with an -s1 electronic configuration are in Group I and all with an -s2 configuration are in
Group II.
1s2 2s2 2p6 3s2 3p6 4s2
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
SCANDIUM
With the lower energy 4s orbital filled, the next
electrons can now fill the 3d orbitals. There are five d
orbitals. They are filled according to Hund’s Rule -
BUT WATCH OUT FOR TWO SPECIAL CASES.
1s2 2s2 2p6 3s2 3p6 4s2 3d1
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
TITANIUM
1s2 2s2 2p6 3s2 3p6 4s2 3d2
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
The 3d orbitals are filled according to Hund’s rule
so the next electron doesn’t pair up but goes
into an empty orbital in the same sub level.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
VANADIUM
The 3d orbitals are filled according to Hund’s rule
so the next electron doesn’t pair up but goes
into an empty orbital in the same sub level.
1s2 2s2 2p6 3s2 3p6 4s2 3d3
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
CHROMIUM
One would expect the configuration of chromium
atoms to end in 4s2 3d4.
To achieve a more stable arrangement of lower energy, one of the 4s
electrons is promoted into the 3d to give six unpaired
electrons with lower repulsion.
1s2 2s2 2p6 3s2 3p6 4s1 3d5
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
MANGANESE
The new electron goes into the 4s to restore its filled
state.
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d5
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
IRON
Orbitals are filled according to Hund’s Rule. They continue to pair up.
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d6
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
COBALT
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d7
Orbitals are filled according to Hund’s Rule. They continue to pair up.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
NICKEL
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d8
Orbitals are filled according to Hund’s Rule. They continue to pair up.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
COPPER
One would expect the configuration of chromium
atoms to end in 4s2 3d9.
To achieve a more stable arrangement of lower energy, one of the 4s
electrons is promoted into the 3d.
1s2 2s2 2p6 3s2 3p6 4s1 3d10
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
ZINC
The electron goes into the 4s to restore its filled state and complete the 3d and
4s orbital filling.
1s2 2s2 2p6 3s2 3p6 4s2 3d10
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
GALLIUM - KRYPTON
The 4p orbitals are filled in exactly the same way as
those in the 2p and 3p sub levels.
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
INC
RE
AS
ING
EN
ER
GY
/ D
IST
AN
CE
FR
OM
NU
CL
EU
STHE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
GALLIUM - KRYPTON
Ga - 4p1
Ge - 4p2
As - 4p3
Se - 4p4
Br - 4p5
Kr - 4p6
Remember that the 4p configurations follow Hund’s
Rule with the electrons remaining unpaired to give
more stability.
Prefix with…
1s2 2s2 2p6 3s2 3p6 4s2 3d10
1s1
1s2
1s2 2s1
1s2 2s2
1s2 2s2 2p1
1s2 2s2 2p2
1s2 2s2 2p3
1s2 2s2 2p4
1s2 2s2 2p5
1s2 2s2 2p6
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2 3p1
1s2 2s2 2p6 3s2 3p2 1s2 2s2 2p6 3s2 3p3 1s2 2s2 2p6 3s2 3p4
1s2 2s2 2p6 3s2 3p5
1s2 2s2 2p6 3s2 3p6
1s2 2s2 2p6 3s2 3p6 4s1
1s2 2s2 2p6 3s2 3p6 4s2 1s2 2s2 2p6 3s2 3p6 4s2 3d1
1s2 2s2 2p6 3s2 3p6 4s2 3d2
1s2 2s2 2p6 3s2 3p6 4s2 3d3
1s2 2s2 2p6 3s2 3p6 4s1 3d5
1s2 2s2 2p6 3s2 3p6 4s2 3d5
1s2 2s2 2p6 3s2 3p6 4s2 3d6
1s2 2s2 2p6 3s2 3p6 4s2 3d7
1s2 2s2 2p6 3s2 3p6 4s2 3d8
1s2 2s2 2p6 3s2 3p6 4s1 3d10
1s2 2s2 2p6 3s2 3p6 4s2 3d10
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
ELECTRONIC CONFIGURATIONS OF ELEMENTS 1-30
2
ELECTRONIC ELECTRONIC CONFIGURATIONCONFIGURATIONthe arrangement of the electron in the atom.Electrons are arranged in Energy Levels or Shells
around the nucleus of an atom.
nucleus
1 3 4s
df
sp
sp d
ps
Atomic orbital
f = 7
d = 5
p = 3
s = 1
1 Atomic orbital = 2 e-
x 2 = 2
x 2 = 6
x 2 = 10
x 2 = 14
2e- 8e- 32e-
Main energy level
Subenergy level
no.of electrons
18e-
Questions1. Which orbital would the electrons fill first? The 2s or 2p orbital?
2. Can you have an electron in between two orbitals?
3. How many d orbitals are there in the d subshell?
4. How many electrons can the p orbital hold?
5. Why can two electrons occupy the same orbital?
1. The 2s orbital would be filled before the 2p orbital because orbitals that are lower in energy are filled first and the 2s orbital is lower in energy than the 2p orbital.
2. You cannot have an electron in between two orbitals. The electron will either be in one orbital or the next.
3. There are 5 d orbitals in the d subshell.4. A p orbital can hold 6 electrons.5. Two electrons can occupy the same orbital because they each have a
different spin. There cannot be two electrons that have the same exact orbital configuration and spin.
1. The 2s orbital would be filled before the 2p orbital because orbitals that are lower in energy are filled first and the 2s orbital is lower in energy than the 2p orbital.
2. You cannot have an electron in between two orbitals. The electron will either be in one orbital or the next.
3. There are 5 d orbitals in the d subshell.4. A p orbital can hold 6 electrons.5. Two electrons can occupy the same orbital because they each have a
different spin. There cannot be two electrons that have the same exact orbital configuration and spin.
1.6 Ionization energy
Draw the electron configuration of oxygen
1s2 2s2 2p41s2 2s2 2p4
If oxygen was ionized, which electron would be removed first?
The antiparallel spin electron has a slightly higher energy. Due to the repulsion from the other electron in the 2px orbital.
The antiparallel spin electron has a slightly higher energy. Due to the repulsion from the other electron in the 2px orbital.
Why?
Will the next electron be easier to remove?
Which one will it be?
The energy needed to remove this electron is known as the First Ionisation Energy (IE)
The energy needed to remove this electron is known as the First Ionisation Energy (IE)
Successive ionisations require more and more energySuccessive ionisations require more and more energy
A logarithmic plot is needed for successive ionisation energies due to the scale. log 1 = 10log 5 = 100,000
Successive Ionisations
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0 2 4 6 8 10 12 14 16 18 20
electron removed
log10 of ionisation
energy
Notice the “jump” in energy needed to remove the 2nd electronNotice the “jump” in energy needed to remove the 2nd electron
Successive ionisation of potassium
Successive ionisation of potassium
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0 2 4 6 8 10 12 14 16 18 20
electron removed
log10 of ionisation
energy
Successive ionisation energies for potassium
The different “jumps” are evidence for the arrangement of electrons in energy levels and sub-levels
level 1
level 2
level 3
level 4
0200400600800
1000120014001600
Na Mg Al Si P S Cl Ar
1st i
on
isat
ion
en
erg
y (k
J/m
ol)
Periodicity of ionisation energy
What trend would you expect ionisation energy to have as you move across a period? B
A
C
What does region “A” represent?
2 x s electrons
2 x s electrons
What does region “B” represent?
3 x p electrons
3 x p electrons
Which three p electrons are these?
px1 py
1 and pz1px
1 py1 and pz
1
What else do you notice about the
graph?
The slopes of A, B and C are almost the same
The slopes of A, B and C are almost the same
Across the periodic table
Describe the graph
What causes the change in the pattern at A = 21
Predict the shape of a graph showing the trend of first ionization energy down a group
Trends of first ionization energy in groups
0
200
400
600
800
1000
Be Mg Ca Sr Ba
1st
ion
isat
ion
en
erg
y
Group 2
Explain why the first ionisation energy decreases as you move down a group
Describe the graph
The initial decrease is steep, but then the graph flattens out
The initial decrease is steep, but then the graph flattens out
ShieldingAs you move down a group, the distance of the outer electrons from the nucleus increases
The inner electrons also shield the outer electrons from the full effect of the positive nuclear charge and repel each other.
They are less tightly bound to the nucleus and so are more easily removed
As you move down a group, the distance of the outer electrons from the nucleus increases
The inner electrons also shield the outer electrons from the full effect of the positive nuclear charge and repel each other.
They are less tightly bound to the nucleus and so are more easily removed
Question
Identify the groups that these atoms belong to
Group 4 – the jump is to remove the 5th electron
Group 4 – the jump is to remove the 5th electron
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Group 2 – the jump is to remove the 3rd electron
Group 2 – the jump is to remove the 3rd electron
Question
Identify the groups that these atoms belong to
Group 3 – the jump is to remove the 4th electron
Group 3 – the jump is to remove the 4th electron
Group 5 – the jump is to remove the 6th electron
Group 5 – the jump is to remove the 6th electron
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
0
2000
4000
6000
8000
10000
12000
14000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Question
Identify the group that this atom belongs to
Group 1 – the jump is to remove the 2nd electron
Group 1 – the jump is to remove the 2nd electron
The number of the electron whose removal causes a jump is one more than the group number that the element belongs to.
The number of the electron whose removal causes a jump is one more than the group number that the element belongs to.
0
2000
4000
6000
8000
10000
12000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Write a general rule for identifying groups from the pattern in ionisation energy
**