12. GROUP 17

Question 1

Why are the melting and boiling points of the halogens relatively low

Answer 1

• they have simple molecular structures

- there are only weak van der Waals’ forces between the molecules

Question 2

What happens to volatility of halogens down the group

Answer 2

volatility decreases as melting points increase

Question 3

Why do van der Waals’ forces increase as the number of electrons increase

Answer 3

• the greater the number of electrons, the greater the opportunities for instantaneous dipoles arising within molecules
• and for induced dipoles to be set up on neighbouring molecules

Question 4

How are halogens oxidising agents

Answer 4

when a halogen reacts with a metal atom, the halogen gains one electron, thus getting reduced

Question 5

What happens to the reactivity going down Group 17

Answer 5

reactivity decreases as electronegativity decreases

Question 6

What happens to the oxidising power of the halogens going down Group 17

Answer 6

oxidising power decreases as electronegativity decreases

Question 7

Why does reactivity decrease down Group 17

Answer 7

• electronegativity decreases down the group
• the atomic radius increases down the group so the distance between the nucleus and outer electrons increases
• an electron entering its outer shell will also experience greater shielding
• there is lesser attraction by the nucleus

Question 8

Why can Cl2 displace Br from NaBr

Answer 8

• chlorine atoms are more electronegative than bromine atoms

- so have a stronger tendency to form negatively charged ions

Question 9

Why does volatility decrease down Group 17

Answer 9

• increasing number of electrons down the group
• van der Waals’ forces increase down the group
• more energy required to break stronger forces