Number that specifies the properties of the atomic orbitals

Tells us the distance from the nucleus and the shape of the orbital

Quantum Number

Electron Configuration

Main level or shell These are the Bohr energy levels

n = 1, n = 2, n = 3 As n increases, the distance from the

nucleus increases

Principal Quantum Number

Each main level is divided into sublevels Four types of sublevels

spdf

Sublevel

Each sublevel is made of orbitals Every orbital can hold 2 electrons

Orbital

s – 1 orbital – 2 electrons p – 3 orbitals – 6 electrons d – 5 orbitals – 10 electrons f – 7 orbitals – 14 electrons

S orbital One spherical

shaped orbital

P orbitals

Three dumbbell shaped One dumbbell in each axis

P Orbitals

D orbitals (5)

F orbitals (7)

Main Level Sublevels Number of Sublevels

Electrons in sublevels

Total Electrons in Main Level

1 s 1 2 2

2 sp

13

26

8

3 spd

135

26

1018

4 spdf

1357

26

1014

32

Arrangement of electrons in an atom Aufbau Principle – electrons fill into an atom

starting with the lowest energy levels

Electron Configuration

Way which the electrons rotate on their axis Pauli Exclusion Principle – in order for two

electrons to occupy the same orbital, they must have opposite spin

Electron Spin

Orbital Diagram

Hund’s Rule – electrons occupy orbitals singly first before doubling up

Write the configuration for each of the below

CSBrNaClKr

Writing Configurations

Valence Electrons Electrons in the last main energy level These are the electrons farthest out on the

atom These will interact with other atoms These are the electrons involved in

chemical reactions There are a maximum of 8 valence

electrons

How to find valence e- Write configuration and count electrons in

last main energy level Examples: Find valence electrons for

CNaPFeAr

Atoms will give up, accept, or share electrons in order to achieve a filled valence shell (8 valence electrons)

Octet Rule

Metallic Character Metals become more reactive (more

metallic in character) as you go down a group

Most metallic elements bottom left corner of the periodic table

Least metallic, top right corner

Ionization Energy Energy required to remove the most

loosely held electron from an atom The greater the ionization energy, the

more strongly the atom holds onto its electrons

M + energy → M+ + e Ionization energy increases as moving

across a period Ionization energy decreases as moving

down a group

Atomic Radius Half of the distance between two adjacent

nuclei Radius decreases across a period (atoms

hold the electrons tightly in) Radius increases down a group