# Quantum Mechanics

## Standard C:2

Students will demonstrate an understanding of atomic structure and nuclear processes.

## Quantum Numbers

• Quantum numbers describe the electron in an atom. ## Principle Quantum Number: n

• Principal quantum number
• Represents the main energy level of an electron
• Maximum # of e- in an energy level = 2n2
• Example: What is the maximum number of electrons that can be in the 6th main energy level?

## Angular Quantum Number: l

• The 2nd quantum number
• Describes the orbital shape within an energy level
• Number of orbital shapes possible in energy level = n (same as principle quantum number)
• n = 1 has 1 shape, n = 2 has 2 shapes, etc.

## Orbital Shapes

Designated s, p, d, f

Level 1: s

Level 2: s, p

Level 3: s, p, d

Level 4: s, p, d, f

Electron Orbitals - s,p & d

## Magnetic Quantum Number: M

• The 3rd quantum number
• Describes the orientation of the orbital in space (on x, y, or z axis)

## Quantum Spin: S

• The 4th quantum number
• Describes the spin of electrons in orbitals
• Ground state: lowest energy arrangement of electrons
• spin up or spin down

## Let's begin Writing Electron Configurations! ## Pauli Exclusion Principle

• At the most two electron per orbital

## Orbitals

s= 1 orbital

p= 3 orbitals

d= 5 orbitals

f= 7 orbitals ## How Many Electrons Can each Sublevel Hold?

s= 1 orbital X 2 e- / orbital = 2e-

p = 3 orbitals x 2 e- /orbital = 6 e-

d = 5 orbitals x 2 e- /orbital = 10 e-

f = 7 orbitals x 2 e- /orbital = 14 e-

## Diagonal Rule (Aufbau Principle)

• Used to show the order in which electrons fill the energy levels and sublevels
• electrons enter the lowest energy level first
• Ex. H
• Ex. B
• Ex. F 