First Ionisation Energy

Question 1

Define the term first ionisation energy

Answer 1

energy required to convert a mole of isolated gaseous atoms into a mole of singly positively charged gaseous ions

Question 2

Where is the decrease in ionisation energy between group 2 and 3?

Answer 2

magnesium and aluminium

Question 3

Why is there a decrease in first ionisation energy between magnesium and aluminium?

Answer 3

magnesium: 1s2 / 2s2 / 2p6 / 3s2
magnesium lose from 3s orbital
aluminium: 1s2 / 2s2 / 2p6/ 3s2/ 3p1
aluminium loses form p orbital
p orbital of slightly higher energy, easier to remove

Question 4

Where is the decrease in first ionisation energy between group 5 and 6?

Answer 4

phosphorous and sulfur

Question 5

Why is there a decrease in first ionisation energy between phosphorous and sulfur?

Answer 5

phosphorous: 1s2 / 2s2 / 2p6 / 3s2 / 3p3
no paired electrons in p orbital (all single)
sulfur: 1s2 / 2s2 / 3s2 / 3p4
paired p orbital electrons repel
sulfur p electron easier to remove