Electron Arrangement

Atoms Review

Name the three particles of the atom and their respective charges are:

a. Proton positive

b. Neutron_ neutral, no charge

c. Electron negative

Atoms Review

The number of protons in one atom of an

element determines the atom’s

identity, and the number of electrons

determines the charge of an element.

Atoms Review

The atomic number tells you the number of protons in one atom of an element. It also tells you the number of electrons in a neutral atom of that element.

The atomic number gives the identity of an element as well as its location on the Periodic Table. No two elements will have the same atomic number.

Valence Electrons

Valence Electrons – are outer energy level electrons.

Label your periodic table with the number of valence

electrons in each group.

12 63 4 75

8

Lewis Structures

Electron Dot Diagrams Show the valence electrons

in an atom. EX: oxygen

O

X

Lewis Structures

Octet Rule Most atoms form bonds in order to obtain _8_ valence electrons Eight valence electrons means the atom has a full outer energy

level. A full outer energy level gives the atom stability. Group 18, the Noble Gases have full outer energy levels.

Learning Check

Where are the electrons in an atom located?

What number tells you the number of electrons in an atom?

What information do Lewis Dot Structures give you?

What is the octet rule?

Electron Configuration

Electrons in Atoms

Electron Configuration

The arrangement of electrons in an atom.

A distinct configuration exists for each atom.

Electron Configuration

Like all systems in nature, electrons in atoms tend to assume arrangements that have the lowest possible energies.

Ground State: the lowest energy arrangement of the electrons.

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.

“Lazy Tenant Rule”

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 # energy level (subtract for d & f)

A/B Group # 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