Chapter 13Chapter 13

Day 2 Day 2

Quantum Numbers and Quantum Numbers and

Electron ConfigurationsElectron Configurations

Bono"The less you know, the more you believe."

Models of the AtomModels of the Atom

DaltonDalton

ThomsonThomson

RutherforRutherfordd

BohrBohr

Neils Bohr model of the Atom:Electrons can be in 1 of many “principle energy levels”, but cannot be in between any of these

energy levels.

Electrons move around the nucleus like planets move around the sun.

Each Principle Energy Level (n) is given a number

n=1n=2n=3

Unfortunately, Bohr’s model of the Hydrogen atom turned out to be incorrect, so a new model was introduced.

Not This! But, This!

What are the Quantum Numbers?What are the Quantum Numbers?

Remember – they give the approximate Remember – they give the approximate location of electrons in an atom.location of electrons in an atom.

They are actually represented by letters.They are actually represented by letters. N – distance (size of orbital)N – distance (size of orbital) l – Shape of orbitall – Shape of orbital m – orientation in space of orbitalm – orientation in space of orbital s – spin of the electrons – spin of the electron

Erwin Schrödinger, using complex mathematics, calculated the probability of where an electron is located.

The probability of an electron in the first principle energy level:

An orbital is drawn that encloses the region where the electron is found 90% of the time.

First Energy Level (n=1) can contain 1 sublevel orbital

Second Energy Level (n=2) can contain 2 sublevel orbitals

Third Energy Level (n=3) can contain 3 sublevel orbitals and so on…

There are many types of sublevels:

Name Shape

s

p

Maximum # of electrons

2

6

Spherical

Dumbell

LowestEnergy

HighestEnergy

Dumbell

Name Shape

d

f

Maximum # of electrons

10

14

LowestEnergy

HighestEnergy

f

What type of sublevel orbital(s) would be found in the first principle energy level (n=1)? How many electrons will it hold?

What type of sublevel orbital(s) would be found in the second principle energy level (n=2)? How many electrons will it hold?

What type of sublevel orbital(s) would be found in the third principle energy level (n=3)? How many electrons will it hold?

The next sublevel is g. How many electrons would it hold?

1s vs 2s vs 3s orbitals

Each sublevel orbital can hold 2 electrons, which have opposite magnetic fields. Therefore, we say that each electron has a spin, which is opposite of each other. This is symbolized by:

Called the Pauli

exclusion principle

Electron ConfigurationsElectron Configurations

Electron ConfigurationsElectron Configurations

Using quantum numbers to give the Using quantum numbers to give the arrangement of electrons around the arrangement of electrons around the nucleus.nucleus.

There are three rules that must be There are three rules that must be followed!followed!

Rule #1Rule #1

AUFBAU principleAUFBAU principle Electrons fill low energy orbitals firstElectrons fill low energy orbitals first

• s,p,d then fs,p,d then f

• Filling orderFilling order 1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

Rule #2Rule #2

Pauli Exclusion PrinciplePauli Exclusion Principle Since there are two possible spins for an Since there are two possible spins for an

electron, no more than two electrons electron, no more than two electrons may fill an orbital.may fill an orbital.• Remember: s = 1 orbital, p = 3 orbitals, d = Remember: s = 1 orbital, p = 3 orbitals, d =

5 orbitals and f = 7 orbitals5 orbitals and f = 7 orbitals

Rule # 3Rule # 3

Hund’s RuleHund’s Rule When multiple shapes are present, When multiple shapes are present,

electrons fill orbitals with parallel spins electrons fill orbitals with parallel spins before pairing up.before pairing up.• Must follow rule #2!Must follow rule #2!

Example 2pExample 2p

Write the following electron Write the following electron configurationsconfigurations

1.1. LiLi

2.2. NaNa

3.3. BeBe

4.4. CC

5.5. SiSi

Using the Periodic TableUsing the Periodic Table

1.1. Read from left to right and top to Read from left to right and top to bottom.bottom.

2.2. Stop when you:Stop when you:a.a. Reach the end of a rowReach the end of a row

b.b. Change colorChange color

c.c. Reach the element of interestReach the element of interest

3.3. Try the following Mg, B, Ne and ClTry the following Mg, B, Ne and Cl

Short-CutShort-Cut

Skip back to the previous Noble Gas (core Skip back to the previous Noble Gas (core electrons) and start with the element after electrons) and start with the element after that.that.

Try: I, U, FeTry: I, U, Fe