ELECTRONS AND THEIR LOCATION

ELECTRON ADDRESSES

RULES TO REMEMBER HEISENBERG UNCERTAINTY PRINCIPLE –

Cannot know the exact location of an electron. Fundamentally impossible to know both the location and momentum/velocity of an electron at the same time.

The quantum mechanical model merely suggests the probability of the electron location.

No circular orbits – Sorry Bohr! Instead: orbitals - the 3-dimensional region

is which there is a high probability of finding an electron in an atom

Aufbau Principle Electrons fill the lowest possible energy

level. Energy levels correspond to period

number on the Periodic Table. How many energy levels are there?

orbitals

Textbook definition: the 3-dimensional region is which there is a high probability of finding an electron in an atom

s on page 371p on page 372d on page 374

Pauli Exclusion Principle No more than two (2) electrons in an

orbital.

Hund’s Rule(s)1. Orbitals of equal energy must fill singly

before doubling. (ex. all d’s must fill with 1 electron each

before the second electron can fill in – like dealing cards)

2. All electrons in singly occupied orbitals have the same spin direction

3. Pairs of electrons in the same orbital have opposite spin.

QUANTUM NUMBERS Describe the electron’s “address” 1st Quantum is the principle quantum –

describes the energy level, or period. 2nd Quantum describes the shape of the

orbitals. s,p,d,f 3rd Quantum describes the orientation of

the orbital 4th Quantum describes the spin of the

electron

Energy Levels

kinds of orbitals

# of each kind

# of electrons

Total # of electrons

Energy levels

kinds of orbitals

# of each kind

# of electrons

Total # of electrons

1 s 1 2 2

Energy levels

Kinds of orbitals

# of each kind

# of electrons

Total # of electrons

1 s 1 2 2

2 sp

13

26

8

Energy levels

Kinds of orbitals

# of each kind

# of electrons

Total # of electrons

1 s 1 2 2

2sp

13

26

8

3spd

135

2610

18

Energy levels

Kinds of orbitals

# of each kind

# of electrons

Total # of electrons

1 s 1 2 2

2 sp

13

26

8

3 sPd

135

2610

18

4 spdf

1357

261014

32

n n kinds odd #’s (total:n2)

2 x # of orbitals

2n2

What do you think the 5th energy level looks like?

The pattern stops – it looks like the 4th energy level

What about 6 & 7?

Quick Quiz A. How many electrons can the p

orbitals hold if filled? B. How many kinds of orbitals are in the

4th energy level? C. What are the orbitals of the 2nd

energy level? D. How many f orbitals are there? E. How many electrons can any one

orbital hold? F. At most, how many electrons in the

2nd energy level?

Orbital Diagrams or Orbital Configurations

Use boxes and arrows to represent electrons in various energy levels.

Boxes must be labeled with regard to energy level and orbitals.

orbital configuration

H

1s

orbital configuration

H

He1s

1s

orbital configurationH

He

Li1s

1s

1s 2s

orbital configurationH

He

Li

Be1s

1s

1s

2s1s

2s

orbital configuration

B

C1s

1s

2s 2p

2p2s

orbital configuration

N1s 2s 2p

Practice

Draw orbital diagrams for elements # 4,6,9,15, and 26

Lewis Dot Structures Element symbol represents atom nucleus and

inner electrons. Dots around the symbol represent valence

(outermost energy level) electrons.

Lewis dot structure

Symbol1

Lewis dot structure

Symbol1 2

Lewis dot structure

Symbol1 23

Lewis dot structure

Symbol1 2

4

3

Lewis dot structure

Symbol1 2

4

53

Lewis dot structure

Symbol1 2

4

536

Lewis dot structure

Symbol1 2

74

536

Lewis dot structure

Symbol1 2

745386

practice

Draw Lewis Dot structures for elements 1-11

Bohr Models Use concentric circles to represent energy

levels and the number of electrons in each.

Bohr model

H1-

Bohr model

Li2-

1-

Bohr model

Ne2-

8-

Bohr model

S2-

8-6-

Bohr model

K

2-

8-8-

1-

Practice Draw Bohr models for elements # 2, 3, 5, 9,

and 16