Unit 1: Electron Configuration

Question 1

Electron Configuration describes… what?

atoms seek ?

atoms with more than 1 electron will have?

Answer 1

• describes how electrons exist in atoms
• all atoms seek lowest possible energy configuration that they can achieve
• all atoms w/ more than 1 electron will have different orbitals, and those orbitals will have different energy

Question 2

Ground State vs Excited State

Answer 2

Ground state – the lowest energy, most stable state of an atom

Excited state – a higher energy state than the ground state

Question 3

3 Principles govern configuration

Answer 3

Aufbau Principle - electrons will occupy the lowest energy orbitals first.

Hunds Rule - electrons will occupy degenerate orbitals (orbitals that have the same energy) 1 electron at a time

Pauli Exclusion Principle - no 2 electrons in the same atom will have the same 4 quantum numbers

Question 4

Aufbau principle

Answer 4

electrons will fill the lowest energy orbitals before filling higher energy orbitals

orbitals named based on subshell

Question 5

L Value N Value

0 s

1 p

2 d

3 f

4

Answer 5

• higher n value and higher L value = higher energy
• within the same n value higher L value = higher energy
• some L values that exist with low n values that have higher energy than values of L that have n higher values.
  
  • Example: 3d > 4s

Question 6

Some exceptions to the filling diagram

Answer 6

higher n order L values much closer in Energy

Energy decreases when orbital is occupied

orbitals can be higher energy than others until full/half full

Question 7

Hunds Rule

Answer 7

Hund’s rule – two electrons in degenerate orbitals will fill separate empty orbitals before pairing

degenerate – existing with equal energies

electrons repel due to charge

2 electrons in the same orbital it increases overall energy

avoid higher energy repulsion by filling orbitals 1 at a time if equal energy

Question 8

Pauli Exclusion Principle

Answer 8

No two electrons in atom have same 4 quantum numbers

Question 9

Looking at examples of orbital filling:

S – 16 electrons n=1: 2; n=2: 8; n=3: 6

Cl – 17 electrons n=1: 2; n=2: 8; n=3: 7

Rb – 37 electrons n=1: 2; n=2: 8; n=3: 18

n=4: 8; n=5: 1

Atom’s valence electrons are number of electrons in the highest value of n

Question 10

Now 118 elements

Total electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶

no atoms are known to exist with n=8 in their ground state configurations.

Question 11

Periodic Table and electron configuration

Answer 11

4 regions, correspond to highest occupied orbitals

s block

p block

d block

f block

Main group from IA – VIIIA: ns1 through ns2np6

Noble gases ns² np⁶

n corresponds to period number

Question 12

Transition elements

d orbitals are n-1 from period

f orbitals are n-2 from period

Can write as different forms:

orbital notation – arrows

electron configuration – exponents

Can write as condensed (simplified) notation – noble gas core

Ex: Na = [Ne]3s1

Paramagnetic/diamagnetic/ferromagnetic