Electron Configuration

Electrons in Atoms

Energy levels, sublevels and orbitals

Energy level(cloud or shell)

Sublevels Orbitals Number of electrons

1 s 1 s orbital 2

2 s, p 1 s orbital

3 p orbitals

8

3 s, p, d 1 s orbital

3 p orbitals

5 d orbitals

18

4, 5, 6, 7 s, p, d, f 1 s orbital

3 p orbitals

5 d orbitals

7 f orbitals

32

s orbitals

1s 2s 3s

Three p Orbitals

px pz py

A. General Rules

Pauli Exclusion Principle

Each orbital can hold TWO electrons

with opposite spins.

A. General Rules

Aufbau Principle

Electrons fill the lowest energy orbitals first.

RIGHTWRONG

A. General Rules

Hund’s Rule

Within a sublevel, place one e- per orbital before pairing them.

“Empty Bus Seat Rule”

O

8e-

Orbital Diagram

Electron Configuration

1s2 2s2 2p4

B. Notation

1s 2s 2p

Shorthand Configuration

S 16e-

Valence Electrons

Core Electrons

S 16e- [Ne] 3s2 3p4

1s2 2s2 2p6 3s2 3p4

B. Notation

Longhand Configuration

© 1998 by Harcourt Brace & Company

sp

d (n-1)

f (n-2)

1234567

67

C. Periodic Patterns

C. Periodic Patterns

Period # (Row) indicates the highest energy level (subtract

for d & f)

Group # (column) Indicates the total # of valence e-

Column within sublevel block # of e- in sublevel

s-block

1st Period

1s11st column of s-block

C. Periodic Patterns

Example - Hydrogen

1

2

3

4

5

6

7

C. Periodic Patterns

Shorthand Configuration Core e-: Go up one row and over to the

Noble Gas. Valence e-: On the next row, fill in the #

of e- in each sublevel.

[Ar] 4s2 3d10 4p2

C. Periodic Patterns

Example - Germanium

Full energy level

1

2

3

4 5

6

7

Full sublevel (s, p, d, f)Half-full sublevel

D. Stability

Electron Configuration Exceptions

Copper

EXPECT: [Ar] 4s2 3d9

ACTUALLY: [Ar] 4s1 3d10

Copper gains stability with a full d-sublevel.

D. Stability

Electron Configuration Exceptions

Chromium

EXPECT: [Ar] 4s2 3d4

ACTUALLY: [Ar] 4s1 3d5

Chromium gains stability with a half-full d-sublevel.

D. Stability

D. Stability

Ion Formation Atoms gain or lose electrons to become

more stable. Isoelectronic with Noble Gases.

D. Stability

Ion Electron Configuration

Find the Noble Gas with the same number of electrons and write its symbol in brackets

EX: Oxygen ion O2- = 10 electrons

= [ Ne ]

Ex: Potassium ion K+ = 18 electrons

= [Ar]

Photoelectric Effect

The emission of electrons from a metal when light shines on the metal only occurs if the photons in the

light have a certain minimum frequency (energy)

Different metals require different minimum frequencies

Line Emission Spectrum

The lowest energy state of an atom is called the ground state

A state in which an atom has a higher potential energy than the ground state is called an excited state

When an excited atom returns to the ground state, it gives off energy, usually in the form of light

Line Emission Spectrum

When this light is shined through a prism, it is separated into a series of specific frequencies of light

The bands of light are known as the line emission spectrum for the element

Line emission spectrum for hydrogen