Periodicity

Question 1

Factors that can affect ionisation energies

Answer 1

• nuclear charge
• Atomic radius (distance from the nucleus/ nuclear attraction)
• shielding

Question 2

second ionisation energy

Answer 2

energy required to remove one electron from each atom in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions

Question 3

What can affect general trend of increasing ionisation energy.

Answer 3

• different period= new sub-shell
  Less/ more shielding
• different orbital
  Higher or lower energy orbital= more/ less energy needed
• spin pair repulsion
  Repulsive force between paired electron in orbital
  Easier to remove= less energy needed

Question 4

trend in first ionisation energy down a group

Answer 4

first ionisation energy decreases down a group
because:
- atomic radius increases
- more inner shells so 
 shielding increases
- nuclear attraction on outer 
 electrons decreases
- first ionisation energy 
 decreases

Question 5

trend in first ionisation energy across a period

Answer 5

first ionisation energy increases across a period
because:
- nuclear charge increases
- same shell/similar shielding
- nuclear attraction increases
- atomic radius decreases
- first ionisation energy 
  increases

Question 6

Across the period, two drops in ionisation energy (even though general trend is increase)

Answer 6

• drop from Be to B

- drop from N to O

Question 7

why does ionisation energy decrease from Be to B

Answer 7

due to filling of p orbital in B

the 2p subshell in boron has a higher energy than the 2s subshell in beryllium so outer electron from B is easier to remove than the 2s electrons, so lower ionisation energy

Question 8

why does ionisation energy drop from N to O

Answer 8

due to electron pairing

in oxygen, the paired electrons in one of the 2p orbitals repel one another (whereas in N each orbital singly occupied) making it easier to remove an electron so lower ionisation energy

Question 9

periodic trend of melting points

Answer 9

melting point increases from group 1 to 4
decreases from 4 to 5 showing change from giant to simple molecular structures

giant structures have strong forces to overcome