Group 2

Question 1

Reactivity in Group 2 with water, acid and oxygen

Answer 1

Reactivity increases down the group for all of them —-> easy to oxidise atom into ion.

Atom becomes bigger, more shielding. Less energy needed to remove electrons.

Acid = salt + hydrogen

2Mg + O2 —-> 2MgO(s)

Barium stored in oil as it is too reactive

Question 2

Physical properties of group 2.

Atomic radius

Answer 2

Atomic radius increases as you go down the group.
Each new element gains a full main level of electrons compared with the one above it.

Question 3

Physical properties of group 2

First IE

Answer 3

First IE of group 2 elements magnesium to barium decreases down the group.

Increases in atomic radius so outermost electrons become further from positive nucleus.
Less electrostatic forces

More shells —-> increase in shielding affects

Question 4

Physical properties of group 2.

Melting points

Answer 4

General trend is that melting points decrease as number shells increase .

Electrons in sea of delocalised electrons further from positive nucleus.

Strength of metallic bond decreases down the group.

Bigger ionic radii—–> less energy needed to break metallic bonds.

Question 5

Which metal doesn’t follow the trend?

Answer 5

Magnesium doesn’t follow trend = hexagonal lattice structure

Requires less energy to separate atoms in hexagonal structure.

Question 6

Solubility of Hydroxides in Group 2

Answer 6

Hydroxides become more soluble down the group.

Increases the pH down the group as concentration of OH- increases.

Mg(OH)2 —> insoluble so used as indigestion tablets. Removes excess stomach acid.

Ca(OH)2 —–> ‘Slaked lime’ used to treat acidity in soil where crops grow, since the crops need a pH close to neutral to grow well.

Question 7

Solubility of sulphates in Group 2

Answer 7

Sulphates become less soluble down the group.

BaSO4 = insoluble as water covers surface of metal.

Used as ‘Barium meal’ = used to diagnose stomach problems as BaSO4 coats the tissues then shows up on the Xray.

Safe as BaSO4 is insoluble so won’t dissolve inside body and cause harm.

Question 8

Using magnesium to extract titanium?

Think about drugs

Answer 8

Titanium —–> less dense, less corrosive and high strength

Alloys used in submarines.

Extracted from its ore — rutile

Add coke

TiO2 + 2Cl2 + 2C —-> TiCl4 + 2CO

Converted into titanium using molten magnesium.

Reaction takes place in inert atmosphere such as argon at 1000C

N2 AND O2 MAKE TI BRITTLE.

Reaction is slow.

Displacement.

Question 9

What happens next??
How is Ti extracted after the reaction with magnesium?

Answer 9

Products cooled

Dilute HCL added to remove unreacted Mg

MgCl2 dissolved in water and Ti is separated.

Mg is reducing agent.

Ti not reducing as it can be brittle.

Ti extraction is expensive.
Mg extraction from ore is expensive.

Exothermic

Question 10

Testing for sulphate ions

Answer 10

Acidified BaCl2 to rates for presence of SO42-

white precipitate formed

Acidified ( to dissolve other anions)

Question 11

Flame gets for group 2 metals.

Answer 11

Be = white

Mg =bright white

Ca = brick red

Sr = Scarlett red

Ba = apple green