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Electron Configuration

Arrangements in the Quantum

Mechanical Model

Electrons are important because they

determine how elements will bond and react

with other elements.

Bohr versus the REAL

THING:

Electron Configuration

Tells us the probable location of an

element’s electrons.

If YOU were an electron….

• Atom = school
• Energy Levels = hallways
• Sub levels = classrooms
• Orbitals = desks
• Electrons = students

Energy Levels –

give the general distance from the nucleus

E N E R G Y

1s

2s

3s

4s

1s

5s

6s

7s

2 p

3 p

4 p

5 p

6 p

7 p

3 d

4 d

5 d

6 d

4f

5f

Color YOUR Periodic Table!

Electron Configuration

1s

Energy Level –

Principal Quantum #

(possibilities are 1-7)

Sublevel

(s, p, d, or f)

of electrons

s: 1 or 2

p: 1-

d: 1-

f: 1-

If you add up all of the electrons, it should equal the atomic #

of the element

3 Main Rules of Orbital Diagrams

1) Aufbau Principle –

Electrons fill orbitals of the lowest energy

first.

The location of the

electron with the

highest energy will

help you identify

the element

Example:

1s

2

2s

2

2p

6

3s

2

3p

6

4s

2

3d

6

Highest energy electron

Element = Iron

3 Main Rules of Orbital Diagrams

2) Hund’s Rule –

Each orbital must have 1 e

before any can

have 2 e

2p

3 Main Rules of Orbital Diagrams

2) Hund’s Rule –

Each orbital must have 1 e

before any can

have 2 e

3) Pauli Exclusion Principle –

Only 2 e

can be found in each orbital, and

they must be spinning opposite directions.

Now write the electron

configuration:

• Fe
• O
• Pb

1s

2

2s

2

2p

6

3s

2

3p

6

4s

2

3d

6

1s

2

2s

2

2p

6

3s

2

3p

6

4s

2

3d

10

4p

6

5s

2

4d

10

5p

6

6s

2

4f

14

5d

10

6p

2

1s

2

2s

2

2p

4

Lewis Dot Structures – show only

the valence electrons.

• Valence Electrons – outershell electrons
• You can count valence electrons by looking

at the group #.

Lewis Dot Structures – show only

the valence electrons.

• Valence Electrons – outershell electrons
• You can count valence electrons by looking

at the group #.

Remember Hund’s Rule when drawing Lewis

Dots BUT draw all “s” electrons (the first 2)

together on the right.

Lewis Dot Structures

Carbon:

C

4 valence e

-

= 4 dots