8.1 Group 2

Question 1

what are the group 2 elements?

Answer 1

alkaline earth metals

Question 2

what is the electronic configuration of a group 2 element?

Answer 2

they have 2 electrons in their outer shell

these 2 electrons are in the s sub-shell

Question 3

why are group 2 metals reducing agents?

Answer 3

group 2 elements are oxidised to form a 2+ ion
they lose 2 electrons from the s sub-shell

Ca ——-> Ca2+ + 2e-

the two electrons lost go on to reduce another element
THEREFORE
group 2 elements are reducing agents

Question 4

group 2 metal + oxygen equation

Answer 4

Ca (s) + O2 (g) ——-> 2CaO (s)

calcium |-> 0 to +2 (oxidised)
oxygen |-> 0 to -2 (reduced)

Question 5

group 2 metal + water equation

Answer 5

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

calcium |-> 0 to +2 (oxidised)
hydrogen |-> +1 to 0 (reduced)

Question 6

general equation for metal + acid?

Answer 6

metal + acid ——-> salt + hydrogen

Question 7

group 2 metal + dilute acid equation

Answer 7

Ca (s) + 2HCl (aq) ——-> CaCl2 (aq) + H2 (g)

calcium |-> 0 to +2 (oxidised)
hydrogen |-> +1 to -0 (reduced)

Question 8

how does reactivity change as you go down group 2?

Answer 8

it increases

Question 9

why does reactivity change as you go down group 2?

Answer 9

because as you go down, the atomic radius decreases and there is increased shielding which leads to a weaker attraction between the positively charged nucleus and the negatively charged electrons

makes it easier to lose an electron

Question 10

what happens to the ionisation energies as you go down group 2?

Answer 10

they decrease

Question 11

group 2 oxide + water

Answer 11

CaO (s) + H2O (l) ——-> Ca2+ (aq) + 2OH- (aq)

Ca2+ + 2OH- ——-> Ca(OH)2

Question 12

what is the trend in alkalinity as you go down group 2?

Answer 12

as the solubility increases the pH increases as there is an increasing concentration of OH- ions

with more OH- ions in the solution the solution is more alkaline as you go down the group

Question 13

what is the trend in solubility as you go down group 2?

Answer 13

solubility increases with the OH- ion concentration increasing

Question 14

how can the trend in alkalinity be shown?

Answer 14

1. add spatula of each group 2 oxide to water in a test tube
2. shake the mixture
3. white precipitate should form in all test tubes
4. measure the pH in each test tube

Question 15

what are the uses of group 2 compounds?

Answer 15

• in agriculture to neutralise soil
• in medicine to act as an antacid

Question 16

how are group 2 compounds used in agriculture?

Answer 16

calcium hydroxide is added to soil in order to increase the pH of acidic soil

Ca(OH)2 + 2H+ ——-> Ca2+ + 2H2O

Question 17

how are group 2 compounds used in medicine?

Answer 17

indigestion tablets contain magnesium hydroxide and calcium carbonates
these bases act as antacids to treat acid indigestion

Mg(OH)2 + 2HCl ——-> MgCl2 + 2H20
or
CaCO3