4A: The elements of Groups 1 and 2

Question 1

State and explain the trend in ionisation energy down group 2.

Answer 1

Decreases.
Same nuclear charge,
shielding and atomic radius increases,
So attraction between the nucleus and outer electrons is weaker.

Question 2

State and explain the trend in reactivity of group 2 elements down the group.

Answer 2

Increases.
1st and 2nd ionisation energies decrease.
Strength of metallic bonds decreases.
So reducing strength increases.

Question 3

Reaction of elements in group 2 with Oxygen

Answer 3

2 M + O₂ -> 2 MO
(Except Barium)

Question 4

Reaction of Ba with Oxygen

Answer 4

Ba + O₂ -> BaO₂ (Barium peroxide)

Question 5

Reaction of elements in group 2 with Chlorine

Answer 5

M + Cl₂ -> MCl₂

Question 6

Reaction of elements in group 2 with Water

Answer 6

M + 2 H₂O -> M(OH)₂ + H₂

Question 7

Reaction of oxides of Group 2 elements with Water

Answer 7

MO + H₂O -> M(OH)₂

Question 8

Reaction of oxides of Group 2 elements with Sulphuric acid

Answer 8

MO + H₂SO₄ -> MSO₄ + H₂O

Question 9

Reaction of hydroxides of Group 2 elements with Nitric acid

Answer 9

M(OH)₂ + 2 HNO₃ -> M(NO₃)₂ + 2 H₂O

Question 10

What is the trend in solubility of the hydroxides of Group 2 elements?

Answer 10

More soluble down the group
Be, Mg - insoluble
Ca - slightly soluble
Sr, Ba - soluble

Question 11

What is the trend in solubility of the sulfates of Group 2 elements?

Answer 11

Less soluble down the group
Be, Mg - soluble
Ca - slightly soluble
Sr, Ba - insoluble

Question 12

State and expain the trend in thermal stability of the nitrates of elements in Groups 1 and 2.

Answer 12

As you go down the group,
The cation has less charge density (same charge, larger radius),
so it polarises the nitrate ion less,
so the N-O bond is weakened less,
so it is more thermally stable.

Question 13

State and expain the trend in thermal stability of the carbonates of elements in Groups 1 and 2.

Answer 13

As you go down the group,
The cation has less charge density (same charge, larger radius),
so it polarises the carbonate ion less,
so the C-O bond is weakened less,
so it is more thermally stable.

Question 14

Desribe how to perform a flame test.

Answer 14

Dip nichrome wire into HCl,
dip into sample,
hold sample over non-luminous blue bunsen flame,
observe flame colour.

Question 15

Why is a nichrome wire used in a flame test?

Answer 15

Does not give a flame colour.

Question 16

Why is the wire dipped into HCl before a flame test?

Answer 16

Cleans the wire
(+ makes it damp so the solid sticks better)

Question 17

Explain the formation of characteristic flame colours by Group 1 and 2
compounds.

Answer 17

Electrons are pushed to a higher energy level.
As they drop back to a lower level they give out energy in the form of light.

Question 18

What are the products from the decomposition of lithium and Group 2 nitrates?

Answer 18

Metal oxide, Nitrogen dioxide, oxygen
Li₂O + 2 NO₂ + 1/2 O₂
MO + 2 NO₂ + 1/2 O₂

Question 19

What are the products from the decomposition of most Group 1 nitrates?

Answer 19

Metal nitrate(III), oxygen
MNO₂ + 1/2 O₂

Question 20

Describe the experimental procedure to show patterns in thermal decomposition of Group 1 and 2 carbonates

Answer 20

Heat the carbonate,
pass the gas through limewater,
measure how long it takes for the limewater to turn cloudy.

Question 21

Describe the experimental procedure to show patterns in thermal decomposition of Group 1 and 2 nitrates

Answer 21

Heat the nitrate,
measure how long it takes for brown gas to form / glowing splint to relight