ELECTRON CONFIGURATIONS
Niels Bohr
The way electrons are arranged around the nucleus.
1s22s22p63s23p64s23d104p65s24d104p65s24d105p66s24f145d106p6…
Chapter 12, page 364
Energy Levels and SublevelsThe emission spectrum for each element has a characteristic set of spectral lines.
This means that the energy levels within the atom must also be characteristic of each element.
When scientists investigated multi-electron atoms, they found that their spectra were far more complex than would be anticipated by the simple set of energy levels predicted for hydrogen.
These spectra have many more lines than the spectrum of hydrogen.
Some lines are grouped close together, and there are big gaps between these groups of lines.
Energy Levels and Sublevels
The big gaps correspond to the energy released when an electron jumps from one energy level to another.
This suggests that sublevels—divisions within a level—exist within a given energy level.
The interpretation of the closely spaced lines is that they represent the movement of electrons from levels that are not very different in energy.
If electrons are distributed over one or more sublevels within an energy level, then these electrons would have only slightly different energies.
The energy sublevels are designated as s, p, d, or f.
Energy Levels and Sublevels
Each energy level has a specific number of sublevels, which is the same as the number of the energy level.
For example, the first energy level has one sublevel. It’s called the 1s sublevel.
The second energy level has two sublevels, the 2s and 2p sublevels
Within a given energy level, the energies of the sublevels, from lowest to highest, are s, p, d, and f.
The third energy level has three sublevels: the 3s, 3p, and 3d sublevels; and the fourth energy level has four sublevels: the 4s, 4p, 4d, and 4f sublevels.
The Distribution of Electrons in Energy LevelsA specific number of electrons can go into each sublevel.
Sublevel Number of Atomic Orbitals
Maximum Number of Electrons
s 1 2p 3 6
d 5 10
f 7 14
Electron Configurations
This most stable arrangement of electrons in orbitals and sublevels is called an electron configuration.
Electrons fill orbitals and sublevels in an orderly fashion beginning with the innermost sublevels and continuing to the outermost.
Get out your PERIODIC TABLES and highlighters / color pencils of different colors
Sections of Periodic Table to Know
f-block
s-block
d-blockp-block
ELECTRON CONFIGURATIONSElectron Configurations represent the location of the electrons in an atom or ion.
1s22s2 2p5
the energy level of the electron (n)
the sublevel
the number of electrons
NOTATIONS OF ELECTRON CONFIGURATIONS Standard Shorthand Orbital Diagrams
WRITING ELECTRON CONFIGURATIONS
1. You always start at the beginning of the periodic table.
2. Use the row number on the periodic table to give you the energy level (or coefficient) to use.
3. Use the block on your periodic table to tell you the sublevel (or letter) to write on your electron configuration.
4. Count across your periodic table until…a. You reach the end of a block or a row.b. You reach your desired element.
This tells you the number of electrons to write (or the exponent).
Write the ground state electron configuration for hydrogen.1s1
Write the complete electron configuration for beryllium.1s22s2
Write the electron configuration for chlorine.1s22s22p63s23p5
ELECTRON CONFIGURATIONS
You try these on your own!
Fluorine
Potassium
1s22s22p5
1s22s22p63s23p64s1
ELECTRON CONFIGURATIONS(CONTAINING THE D-SUBLEVEL)
The energy level of d-sublevel will ALWAYS be one less than the row
or period number.
Write the electron configuration for titanium (Ti).s1s 22 22p63s23p64s23d2
Write the electron configuration for iron (Fe).s1s 22 22p63s23p64s23d6
Write the electron configuration for bromine (Br).s1s 22 22p63s23p64s23d104p5
You try these on your own! Tellurium (Te)
Silver (Ag)
1s22s22p63s23p64s23d104p65s24d105p4
1s22s22p63s23p64s23d104p65s24d9
SHORT-HAND NOTATION
[Ne]3s23p2
Uses a noble gas (Group 18) to represent the innermost electrons.
Outermost electrons are
represented the same way.
Hint:To find the noble gas, look at the noble gas from the previous row or the row above the element.
Shorthand Electron Configuration (S.E.C.)
To write S.E.C. for an element: 1. Put symbol of noble gas that precedes
element in brackets. 2. Continue writing e– config. from that point.
Write the noble gas electron configuration for silicon.[Ne] s23 3p2
Write the noble gas electron configuration for zinc.[Ar] s24 3d10
NOBLE GAS ELECTRON CONFIGURATIONS
You try these on your own!
Barium (Ba)
Antimony (Sb)
[Xe]6s2
[Kr]5s24d105p3
O
Orbital Diagrams
…show spins of e– and which orbital each is in
1s 2s 2p 3s 3p
1s 2s 2p 3s 3pP
http://genchem1.chem.okstate.edu/ccli/CCLIDefault.html
ORBITAL DIAGRAMS/ELECTRON CONFIGURATION
hydrogen
helium
carbon
1s1
1s2
1s2 2s2 2p4
VALENCE ELECTRONS
Valence electrons are electrons found on the highest energy level.
• They are always “s” or “s” and “p” electrons. • There can be no more than eight valance
electrons.
1s22s22p63s23p2
What is the highest energy level?n =3 or third energy level
How many electrons are on the highest energy level?4 electrons
How many valence electrons are in this element?4 electrons
SAMPLE QUESTIONS
Write the electron configuration (the long way or short hand notation) for the following elements. For each element, determine the number of valence electrons.1. Calcium
2. Nitrogen
3. Arsenic
1s22s22p63s23p64s2 or [Ar]4s2
2 valence electrons
1s22s22p3 or [Ne] 2s22p3
5 valence electrons
1s22s22p63s23p64s23d104p3 or [Ar] 4s23d104p3
5 valence electrons
LEWIS DOT DIAGRAMS
Element Symbol
One Dot for Each Valence Electron
LEWIS STRUCTURES1) Find your element on the periodic table.2) Determine the number of valence electrons.3) This is how many electrons you will draw.
LEWIS STRUCTURES
• Find out which group (column) your element is in.
• This will tell you the number of valence electrons your element has.
• You will only draw the valence electrons.
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GROUPS - REVIEW
•Each column is called a “group”
•Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.
Group 1 = 1 electronGroup 2 = 2 electrons
Group 8 = 8 electrons
Except for He, it has 2 electrons
•The electrons in the outer shell are called “valence electrons”
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3, 4, 5, 6, 7
How-To: Nitrogen1. Start with the chemical symbol.
N
2. Determine the number of valence electrons.3. Place the first dot on the right side. 4. Place the other dots counterclockwise around the chemical symbol.5. Continue in the same direction until there is at least one dot on the four sides6. Place a second dot for each side as needed following in the same direction.
LEWIS STRUCTURES1) Write the element
symbol.2) Carbon is in the 4th
group, so it has 4 valence electrons.
3) Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol.
C
LEWIS STRUCTURES
P
LEWIS STRUCTURES
Ca
SAMPLE QUESTIONS
How to Place the Dot on Any Symbol
Draw the Lewis dot diagrams for the following elements.
Silicon
Sodium
Iodine
X Si
Na
I
