Honors Chemistry September 16, 2013. Preview of Lesson Where are electrons found around the nucleus?...

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Honors Chemistry

September 16, 2013

Preview of Lesson• Where are electrons found around the nucleus?• 4 different shaped orbitals (x-ray diffraction and

electron microscopy)– s, p, d, f

• Higher energy levels have more shapes• Each orbital can hold 2 e-

– Locate the e- 90% of the time

• Orbital is also called Subshells

Bohr's ModelBohr's Model

• Model ofelectronsin fixedorbits to explain quantization Figure 6.14

• Transitionsbetweenorbitsemits orabsorbslight 07m07an107m07an1

07m07an1.mov.lnk

Observation of unique line spectra led to Quantum Theory

Nucleus

Second

FourthE=hν

Orbital Diagrams and Electron Configurations

• n = Principle quantum number • Describes the energy level the electron occupies (PT)

n = 2n = 3n = 4

Orbital Energy Levels

Ground stateGround state

Excited statesExcited states

• Shape of orbitaldesignated by theletters

s, p, d, f

Shapes of OrbitalsShapes of Orbitals• Shape of orbital designated by the letters

s, p, d, f• Orbitals have

different shapes

The s orbital has a spherical shape centered aroundthe origin of the three axes in space.

s Orbital shapes Orbital shape

There are three dumbbell-shaped p orbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.

p orbital shapep orbital shape

Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of “double dumbells”

…and a “dumbell with a donut”!

d orbital d orbital shapesshapes

Shape of f orbitalsShape of f orbitals

CombinationCombination

of electronof electron

microscopymicroscopy

and x-rayand x-ray

diffractiondiffraction

producedproduced

image ofimage of

orbitalsorbitals

Sets of Orbitals (Subshells)Sets of Orbitals (Subshells)

• Depending on the type of orbital, we find that they occur in sets differing in their orientationsets differing in their orientation in space in space

• s - set of 1• p - set of 3• d - set of 5 • f - set of 7

• Label P.T.

Orbitals.exe.lnk

Sizes of orbitals• Size depends on the value of n

• Orbitals with the same n are about the same size

Check for understanding

• What is the principal quantum number for Ar?• What are the subshells?• How many sets of electrons are found in each

subshell?

Electron Configurations of Some Atoms(Stop P1 + 5)

• The firstten elements

1s2 2s1

1s2 2s2

1s2 2s2 2p1

1s2 2s2 2p2

1s2 2s2 2p3

1s2 2s2 2p4

1s2 2s2 2p5

1s2 2s2 2p6

Shorthand Notation for OrbitalsShorthand Notation for Orbitals• Combinations of first two quantum numbers;

number of orbital types equals the shell number (n).

• 1s• 2s, 2p• 3s, 3p, 3d• 4s, 4p, 4d, 4f• 5s, 5p, 5d, 5f, (5g)• 6s, 6p, 6d, 6f, (6g, 6h)

Refer to electron configuration worksheet

Agenda

• Brain Teaser• Grade Worksheet• Review

– Writing Electron Configuration

• Notes: Orbital Diagram• Homework

– Short Hand Electron Configuration– Orbital Diagram

Grade Homework

• Refer to Worksheet (Arrangement of Electrons I)

Check for understanding (P6)

• What is the principal quantum number for Ar?• What are the subshells?• How many sets of electrons are found in each

subshell?

Aufbau Principle

• Aufbau Principle: start with the nucleus and empty orbitals, then “build” up the electron configuration using orbitals of increasing energy

Aufbau.exe

Electron ConfigurationsElectron Configurations

• Electron Spin and Pauli Exclusion Principle:– Only two electrons can occupy a

single orbital and they must have opposite spins

Electron Configurations

• Hund's Rule: –When filling a subshell, such as the set

of 3 p orbitals, place 1 electron in each before pairing up electrons in a single orbital

Electron Configurations

• Arrangement of electrons in the orbitals is called the electron configuration of the atom

• The ground state configuration can be predicted, using the Aufbau Principle, the Pauli Exclusion Principle, and Hund’s Rule.

Electron configurationsElectron configurations Filling _ rules.exeFilling _ rules.exe

How do we know what the filling order is?

• What chemistry tool might we rely on?

Electron Configurations and the Periodic Table

• Valence electron configurations repeat down a group

aufbau.exe.lnk

Ground state electron configurations

• Example: Li– atomic number = 3– nucleus has 3 protons– neutral atom has 3 electrons

• 2 electrons in 1s orbital, 1 electron in 2s orbital

Different ways to show electron configuration

Read this “one s two”not “one s squared”

Li 1s2 2s1

Energy level diagram Box notation

Spectroscopic notation

Write the superscript 1.Don’t leave it blank

Practice

• Review (on separate sheet of paper)– Electron Configuration– Orbital Diagram

• Electron configuration worksheet

Using the Periodic Table

The last subshell in the electron configuration is one of these(row #) s (row # – 1) d(row #) p (row # – 2) f

The f-block is inserted into to the d-block

Electron configuration of O• Atomic number of O = 8 so neutral atom has 8 e–

Electron configuration of Co• Atomic number of Co = 27 so neutral atom has 27 e–

Simplifying electron configurations• Build on the atom’s noble gas core

• He 1s2

O 1s22s22p4

O [He]2s22p4

• Ar 1s22s22p63s23p6

Co 1s22s22p63s23p64s23d7

Co [Ar]4s23d7

1s 2s 2p

Noble Gases

• Far right of the periodic table• These elements are extremely unreactive or

inert• They rarely form compounds with other

elements

Noble Gas electron configurations

• What is the electron configurations for Neon

• Abbreviated way to write configurations– Start with full outer shell then add on

• Br• Ba

Noble Gases

• Neon- emits brilliant light when stimulated by electricity – neon signs- 4th most abundant element in the universe.

• Helium- light non reactive gas- used balloons- inexpensive, plentiful and harmless

• Radon- radioactive gas- can cause cancer- colorless, odorless emitted from for certain rocks underground

• Properties of atoms correlate with the number and energy of electrons

• Electron configurations are used to summarize the distribution of electrons among the various orbitals

Why are we doing all of this?Why are we doing all of this?

PracticePractice

3-3 PracticeWrite the complete electron

configurations and noble gas shorthand #1-4

Practice

1. Refer to a periodic table and write the electron configurations of these atoms.

2. Write the configurations using shorthand notation.

• Zn

• Cs

The f-block is inserted into to the d-block

Find the electron configuration of Au

• Locate Au on the periodic table

• Au [Xe]• The noble gas core is Xe

• Au [Xe]6s2

• The noble gas core is Xe• From Xe, go 2 spaces across the s-block in the 6th row 6s2

• Au [Xe]6s24f14

• Then detour to go 14 spaces across the f-block 4f14

– note: for the f-block, n = row – 2 = 6 – 2 = 4

• Au [Xe]6s24f145d9

• Then detour to go 14 spaces across the f-block 4f14

– note: for the f-block, n = row – 2 = 6 – 2 = 4• Finally go 9 spaces into the d-block on the 6th row 5d9

– note: for the d-block, n = row – 1 = 6 – 1 = 5

Electron configuration of ions

• What is an ion?• How many electrons does Cl1- have?

– What is the electron configuration for the chloride ion?

• How many electrons does Ca2+ have?– What is the electron configuration for the calcium

• What do you notice?

Practice

• Draw the orbital diagram for sulfur.– What ion does sulfur want to form and why?

• Draw the orbital diagram for Potassium.– What ion does sulfur want to form and why?

What does this mean

• Properties of atoms correlate with the number and energy of electrons

• Atoms like to have full outer shells.

Why is this important

Valence electrons• Electrons in the outermost energy level

– Where all the action occurs

Practice

• Whiteboard - Atomic Structure (continued)

Team• Write the electron configuration for silver.• Write the noble gas configuration for silver.• What element has the following electron configuration?

1s22s22p6 3s23p64s23d4

Today we use aspects of line spectrum to identify elements,

compounds and mixtures?

• UV-Vis Spectrometer– Distances and types of stars– Blood test- carbon monoxide poisoning– Mobile weapons detectors– Chlorophyll

How we determine these energy levels?

Honors Chemistry September 16, 2013. Preview of Lesson Where are electrons found around the nucleus?...

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