2A.3 Atomic Orbitals and Electronic Configurations

Orbital

Region within an atom that can hold up to 2 electrons with opposite spins

Why different quantum shells have different energies

Quantum shells are made of subshells

Shape of s orbital

Spherical

Shape of p orbital

elongated (dumbell/figure 8)

Properties of orbitals in sub shells

- Take single electron before pairing up

- Pair up with two electrons of opposite spins

Subshells in 1st shell

s

Subshells in 2nd shell

s,p

Subshells in 3rd shell

s,p,d

Subshells in 4th shell

s,p,d,f

Electrons in s subshell

2

Electrons in p subshell

6

Electrons in d subshell

10

Electrons in f subshell

14

Electron density

The relative probability of finding an electron in a certain region of space.

Hund's rule

Electrons occupy orbitals singly / in different axes before pairing takes place

Pauli exclusion principle

Two electrons cannot occupy same orbital unless they have opposite spins / electrons pair with electrons of opposite spins after occupying orbitals in different axes singly

Electron properties

- 1/1840 relative mass

- -1 relative charge

- has angular momentum

Protons attract?

Electrons

Types of spin in electrons

- up-spin

- down-spin

Up-spin

Angular momentum of electron in upward direction

Down-spin

Angular momentum of electron in downward direction

How to draw electrons in boxes diagram

- boxes of same subshell close together

- each box occupy 2 electrons

- first up-spin occupy boxes singly in the subshell

- Then down-spin pair with electrons in half-filled boxes

Shape of p subshell

Figure 8 on each axis

Electrons in p orbital

2

Electrons in 1st quantum shell

2

Electrons in 2nd quantum shell

8

Electrons in 3rd quantum shells

18

Why hund's rule occurs

- two electrons in single orbital would increase electron-electron repulsion & orbital energies of electrons

- preferred electronic configuration is one with lowest energy

What arrows indicate in boxes diagram

spin electron has

What does x,y,z letters mean in boxes diagram

cartesian axis on which orbital exists

Electron filling order when writing electronic configuration

1s 2s 2p 3s 3p 4s 3d 4d