2.2.2 Sub-shells and Energy Levels

Question 1

What evidence is there for the existence of shells?

Answer 1

Spectral lines (Bohr atomic model) are directly related to the position of electrons in shells and sub-shells.

Question 2

Why are orbitals called s,p,d and f?

Answer 2

S - sharp
P - principal
D - diffuse
F - fundamental

Question 3

What is the Aufbau principle?

Answer 3

German, ‘building up’ principle

1. The lowest available energy level is filled first
2. Each energy level must be full before the next, higher energy level starts to fill - so the 4s orbital will fill before the 3d orbital (important exception), because it has a slightly lower energy level.
3. Paired electrons have opposite spins (one up arrow and one down) and will be as spaced out as possible in x principal no.

Question 4

What does the notation ‘nx^y ‘ mean? What are sub-shells made up of?

Answer 4

n - shell number
x - type of orbital
y - no. of electrons making up the sub-shell
Sub-shells are made up of several orbitals, each with the same energy level.

Question 5

What happens to electron configuration when the atom is ionised?

Answer 5

The electron in the highest energy level would be removed. ‘Last in, first out’

Question 6

What is the electron configuration of B (5 electrons)?

Answer 6

1s^22s^22p^1 (occupies half a px orbital)

Question 7

What is the electron configuration of C (6 electrons)?

Answer 7

1s^22s^22p^2 (occupies half a px orbital and half a py orbital, as electrons spread out as far as possible - both negative so repel)

Question 8

What is the electron configuration of N (7 electrons)?

Answer 8

1s^22s^22p^3 (occupies half a px, half a py and half a pz orbital)

Question 9

What is the electron configuration of O (8 electrons)?

Answer 9

1s^22s^22p^4 - can go up to 6 (occupies a px orbital, half a pz and half a py)