3.2.2 - Group 2: Alkaline Earth Metals

Question 1

Group 2 metals _______ to ___ _____.

Answer 1

Group 2 metals oxidise to +2 ions.

Question 2

Atomic radius _______ down group 2.

Answer 2

Atomic radius increases down group 2.

Question 3

Reactivity _______ down group 2.

Answer 3

Reactivity increases down group 2.

Question 4

First ionisation energies _______ down group 2.

Answer 4

First ionisation energies decrease down group 2.

Question 5

What kind of bonding do group 2 elements undergo?

Answer 5

Metallic bonding - between +2 ions and a sea of delocalised ions

Question 6

Bonding ______ in strength down the group. Why?

Answer 6

Decreases: atomic radii increase, but each metal atom still loses only two electrons (to form a +2 ion). This means that there is less attraction between the delocalised electrons and the positive ion nuclei.

Question 7

There is a ______ charge density on the ions going down the group.

Answer 7

There is a lower charge density on the ions going down the group.

Question 8

Exception of bpt trend down group 2? Why?

Answer 8

Magnesium: the bpt of magnesium is lower than that of calcium. This is because of magnesium’s irregular crystal structure.

Question 9

State the general equation for group 2 elements reacting with water. Water acts as an _______ ______.

Answer 9

M (s) + 2H2O (l) -> M(OH)2 (aq) + H2 (g)

Water acts as an oxidising agent.

Question 10

State the equation for magnesium reacting with water vapour.

Answer 10

Mg (s) + H2O (g) -> MgO (s) + H2(g)

Question 11

Magnesium reacts very quickly with cold water. True/false?

Answer 11

False - magnesium reacts very slowly with cold water, but very rapidly with steam.

Question 12

Trend in the solubility of group 2 metal/hydroxide anion compounds down the group?

Answer 12

Solubility of metal hydroxide compounds increases down the group

Question 13

Magnesium hydroxide is soluble. True/false?

Answer 13

False: magnesium hydroxide is sparingly soluble and is a solid suspension in water.

Question 14

Ca(OH)2 is _______ soluble.

Answer 14

Sparingly soluble.

Question 15

Use of calcium hydroxide?

Answer 15

Lime water solution! Also slaked lime and neutralises acidic soils.

Question 16

Sr(OH)2 is insoluble. True/false?

Answer 16

False - Sr(OH)2 is soluble.

Question 17

Ba(OH)2 dissolves to form what? State the equation.

Answer 17

A very alkaline solution: Ba(OH)2 (s) + aq -> Ba2+ (aq) + 2OH- (aq)

Question 18

Trend in the solubility of group 2 metal/sulfate anion compounds down the group?

Answer 18

Solubility of metal sulfate compounds decreases down the group

Question 19

Use of barium sulfate, BaSO4?

Answer 19

Barium meals - taken by patients with gastric problems, as it is opaque to x-rays so will absorb them and highlight blockages on an x-ray of the digestive system.

Question 20

Is BaSO4 safe to take orally?

Answer 20

Yes - it is insoluble so does not enter the bloodstream.

Question 21

Use and name for Mg(OH)2?

Answer 21

‘Milk of magnesia’: an antacid that treats heartburn.

Question 22

What is the neutralisation equation?

Answer 22

H+ + OH- -> H2O

Question 23

Test for sulfate ions, SO4^2-?

Answer 23

1. Add HCl or HNO3 (to react with and remove sulfites and carbonates that would form a false positive).
2. Add BaCl2.
3. Positive: white precipitate of BaSO4.

Question 24

Calcium, strontium and barium react in the same way as magnesium with water vapour, but less vigorously. True/false?

Answer 24

False: calcium, strontium and barium react in the same way as magnesium with water vapour, but MORE vigorously.