QUANTUM NUMBERS

• Quantum numbers - help to describe the probable location of an electron in an atom or ion - Like the electrons address

1. (n) principal ~ main energy level

2. (l) angular momentum ~ sublevel where the electron is found

3. (ml )magnetic ~ the orbital where the electron is found

4. (ms) spin ~ direction the electron is spinning

PRINCIPAL QUANTUM NUMBER ( n)

• Tells what energy level in the electron cloud the electron is found on

• There are 7 energy levels

• They correspond to the 7 periods on the PTE.

n = 1n = 2n = 3n = 4n = 5

Angular Momentum quantum number ( l )

sl=0

pl=1

dl=2

•AKA: The sublevels

•There are 4 different shaped sublevels

•The sub-levels are named s, p, d, and f.

fl=3

Magnetic QUANTUM NUMBER (m l )

• Magnetic quantum number- the orbital in which the electron is found in

• Each orbital can hold maximum 2 electrons.– S has 1 orbital

– p has 3 orbitals

– d has 5 orbitals

– f has 7 orbitals

P sublevel ( 3 orbitals)

s sublevel ( 1 orbital)

ml = 0

ml = 0 ml = -1 ml = +1

d sublevel ( 5 orbitals)

ml = -1 ml = 0ml = -2 ml = +2ml = +1

f sublevel ( 7 orbitals)

ml = -1

ml = -2

ml = -3

ml = +2

ml = +3

ml = +1

ml = 0

Spin QUANTUM NUMBER (m s )

• + ½ or – ½ • Each electron in an orbital will spin in the opposite direction - Clockwise

and counterclockwise

EX: Finding an electron’s home:

Address: n= 3 l = 1 ml = 0 ms = + ½

Energy level 3, p-sublevel, 2nd orbital, 1st electron in the orbital spinning clockwise

Address: n = 4 l = 2 ml = +1 ms = - ½

Energy level 4, d-sublevel, 4th orbital, 2nd electron in orbital spinning counterclockwise

Pauli Exclusion Principle

• No two electrons within an atom (or ion) can have the same four quantum numbers.

• If two electrons are in the same energy level, the same sublevel, and the same orbital, they must spin in opposite directions.

• A.K.A. Electrons cannot have the EXACT same address!

• Electrons will occupy those orbitals with the lowest energy, closest to the nucleus before filling orbitals further away.

• Electrons will fill unoccupied orbitals before they pair up in an orbital.

• AKA: Like riding the bus home!

Orbitals and the Periodic Tables, p, d, and f blocks

http://www.ptable.com/

Order of filling…electrons fill the orbitals closest to the nucleus first

s

s 3p 3d

s 2p

s 4p 4d 4f

s 5p 5d 5f

s 6p 6d 6f

s 7p 7d 7f

1

2

3

4

5

6

7

Order of filling…electrons fill the orbitals closest to the nucleus first

s

s 3p 3d

s 2p

s 4p 4d 4f

s 5p 5d 5f

s 6p 6d 6f

s 7p 7d 7f

1

2

3

4

5

6

7

Orbital Diagrams

• Graphical representation of the electrons in an atom’s electron cloud

• An arrow represents one electron

• Direction of arrow shows spin and which orbital within a sublevel

• Must follow Hund’s rule and Aufbau’s principle when placing electrons in orbitals

Electron Configurations

• Diagram that shows the following:

Principle quantum number ( whole number)

Angular momentum quantum number ( letter of

sublevel)

Number of electrons in an orbital ( subscript)

• Must follow order of filling (Aufbau principle)

• Used to determine the element and electrons on last

energy level