Electron structure

Chapter 5

Number of electrons that can fill the first 4 shells

Eectrons in a shell is given by:
2n², where n = shell number

First four shells:

• n = 1 → 2(1)² = 2 electrons

• n = 2 → 2(2)² = 8 electrons

• n = 3 → 2(3)² = 18 electrons

• n = 4 → 2(4)² = 32 electrons

Atomic orbital

Region around the nucleus where up to two electrons can be held with opposite spin

These orbitals make up subshells which make up shell

S, P, and D orbitals

• s-sub-shell:

  • 1 orbital

  • holds 2 electrons

• p-sub-shell:

  • 3 orbitals

  • holds 6 electrons

• d-sub-shell:

  • 5 orbitals

  • holds 10 electrons

S and P orbital shape

Filling of orbitals

Order:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p my sister was like oh
In order of lowest energy to highest energy

Electrons lost higher energy first and when 3d join 4s becomes higher energy so 4s lost before 3d

Electrons fill singly first in orbitals of equal energy

• Only after all are singly occupied do they pair up

• This is Hund’s rule