2.2 Group 2

Question 1

Explain the I.E. graph pattern of Group 3

Answer 1

First Ionisation energy increases across group 3 because of increased nuclear charge, decreased atomic radius and same electron shielding means more energy is needs to remove the first electron.

Dips at Al because: outer electron is in a 3p orbital, higher energy than 3s orbital → less energy needed to remove electron

Dips at S because one 3p orbital contains two electrons → repulsion between paired electrons → less energy needed to remove one

Question 2

What happens to the first ionisation energy as you

go down group 2? Why?

Answer 2

Decreases because: number of filled electron shells increases down the group → increased shielding, increased atomic radius → weaker force between outer electron and nucleus → less energy needed to remove electron

Question 3

How does reactivity with water change as you go

down group 2?

Answer 3

Increases (Mg least → Ba most) Because outer electrons further from nucleus and more electron shielding, so electrons are lost more easily

Question 4

What is the trend in hydroxide solubility down group 2?

Answer 4

Increases down the group

Mg(OH)₂ is almost insoluble

Ba(OH)₂ creates a strong alkaline solution

Question 5

What is the trend in sulphate solubility down group 2?

Answer 5

Decreases down group

MgSO₄ is soluble

BaSO₄ is insoluble

Question 6

What is the trend in melting point down group 2? Why?

Answer 6

Decreases down group because sea of delocalised electrons is further from the positive charge of the nucleus → weaker metallic bonds / forces of attraction which take less energy to weaken

Question 7

What is the trend in atomic radius down group 2?

Answer 7

Increases as there are more occupied electron shells down the group

Question 8

What are flue gases?

Answer 8

Gases produced by power stations which are harmful to the environment

Question 9

What is Ca(OH)2 used for? Write an equation related to one of its uses

Answer 9

Used to neutralise soil

Question 10

What is Mg(OH)2 used for?

Answer 10

Milk of magnesia - antacid to treat indigestion, heartburn, wind etc.

Question 11

What is a use of BaSO4 ? Why is it safe?

Answer 11

In barium meals to outline gut in X-rays Ba²+ is toxic but is fine as barium sulphate is insoluble

Question 12

How can BaCl2 be used to test for sulfate ions?

Answer 12

Add to sample with HCl, white ppt will form if sulfate ions present