Group 2, the alkaline earth metals

Question 1

describe the physical appearance of the Group 2 metals in comparison to Group 1

Answer 1

harder and denser than the Group 1 metals
higher melting points, surface is covered in a layer of oxide

Question 2

describe the trend in reactivity down the group

Answer 2

reactivity increases down the group

Question 3

what is the trend of ionisation energy for group 2 elements ?

Answer 3

extra shells so more shielding so weaker attraction between the nucleus and the outer electrons - easier to remove the outer electrons so less energy needed

Question 4

compare the sizes of a K+ ion and a Ca 2+ ion

Answer 4

Ca 2+ ion is smaller than a K + ion because the effective nuclear charge is 2 + compared to 1+ for K + so the remaining electrons are held more closely

Question 5

what is the oxidation state of Group 2 metals in their compounds ?

Answer 5

+ 2

Question 6

what types of agents is Group 2 metals ?

Answer 6

reducing agents

Question 7

which metal in Group 2 is not a reducing agent ?

Answer 7

beryllium as they readily give up their two s electrons to form M 2+ ions

Question 8

why is beryllium not a typical Group 2 element ?

Answer 8

the small size of its ion means that it has a much higher polarizing power than other Group 2 ions so its compounds have different chemical characteristics

Question 9

what does group 2 elements produce in the reaction with oxygen ?

Answer 9

metal oxides - bases

Question 10

group 2 oxides
- state the reaction of magnesium oxide and beryllium oxide

Answer 10

magnesium oxide - reacts very slowly and the hydroxide barely dissolves
beryllium oxide - does not react with water at all and the hydroxide is insoluble

Question 11

as we go down the group, why do the group 2 oxides become more strongly alkaline ?

Answer 11

as the hydroxides become more soluble

Question 12

how does oxides react with water ?

Answer 12

readily with water to make hydroxides which dissociate to form OH- ions

Question 13

what does reaction with water for group 2 elements produce ?

Answer 13

metal hydroxides - bases

Question 14

reactions with water - group 2 elements
- example

Answer 14

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

Question 15

an increase of number of protons decreases down the group, what does the the shielding effect do ?

Answer 15

it overrides an increase in positive charge

Question 16

Mg reacts slowly in cold water but more vigoursly in steam what does it produce ?

Answer 16

magnesium oxide instead of a hydroxide so the equation would be 2H2O(aq) not 2H2O(l)

Question 17

what does group 2 elements produce when reacting with chlorine ?

Answer 17

metal chlorides - chlorides

Question 18

reactions with chlorine - group 2 elements
- write the balanced equation for the reaction between beryllium and chlorine

Answer 18

Be (s) + CI2 (g) -> BeCI2 (s)

Question 19

the oxides
- write the balanced symbol equation for the reaction between calcium oxide and nitric acid

Answer 19

CaO (s) + 2HNO3 (aq) -> Ca(NO3)2 (aq) + H2O (l)

Question 20

the hydroxides - state the solubility
- magnesium hydroxides
- calcium hydroxide
- barium hydroxides

Answer 20

magnesium hydroxides - insoluble in water
calcium hydroxide - slightly soluble in water
barium hydroxides - the most soluble hydroxide

Question 21

write the balanced equation for the thermal decomposition of calcium carbonate

Answer 21

CaCO3 (s) -> CaO (s) + CO2 (g)

Question 22

describe the trend in thermal stability down the group

Answer 22

increases down the group

Question 23

write the balanced symbol equation for the thermal decomposition of magnesium nitrate

Answer 23

2Mg(NO3)2 (s) -> MgO (s) + 4NO2 (g) + O2 (g)

Question 24

describe the trend in thermal stability group 2

Answer 24

increases down the group

Question 25

describe the trend in solubility in Group 2 sulfates down the group

Answer 25

• as the cation gets larger, it has a low charge stability
• it becomes less attracted to the polar water molecules

Question 26

flame colors
metal ion
calcium
strontium
barium

Answer 26

calcium - brick red
strontium - crimson
barium - pale green

Question 27

what is thermal stability ?

Answer 27

an indication of the ease with which compounds decompose on heating

Question 28

polarizing power - define

Answer 28

indication of the extent to which a positive table is able to distort the electron cloud around a negative ions

Question 29

explain why the thermal stability of carbonates and nitrates increases down the Group 2

Answer 29

• the carbonates ion becomes polarized
• as the positive ions get bigger as you go down the group, they have the less effect on carbonate ions near them
• to compensate for that, you heat the compound more in order to persuade the O2 to break free + leave the metal oxide

Question 30

describe the type of ion with the greatest polarizing power in terms of charge and size

Answer 30

charge: large
size: small

Question 31

neutralisation of group 2 oxides - example

Answer 31

CaO + 2HCI -> CaCI2 +H2O base + acid -> salt + water

Question 32

neutralisation of group 2 hydroxides - example

Answer 32

Ca(OH)2 + 2HCI -> CaCI2 + 2H2O
base + acid -> salt + water

Question 33

if the anion has a double charge how soluble is it as we go down the group ?

Answer 33

less

Question 34

is the anion has a single charge how soluble is it as we go down the group ?

Answer 34

more soluble

Question 35

what does carbonates break down into during thermal decomposition ?

Answer 35

metal oxides and carbon dioxide

Question 36

what does nitrates break into during thermal decomposition ?

Answer 36

metal oxides, nitrogen dioxide and oxygen

Question 37

write the balanced equation for the thermal decomposition of calcium nitrate

Answer 37

2Ca(NO3)2 (s) -> 2CaO (s) + 4NO2 (g) + O2 (g)

Question 38

when the carbonate/ nitrate ion is nearby positive 2 metal ions what happens ?

Answer 38

it has a large electron cloud that can be distorted

Question 39

explain why group 2 metal ions have a low charge density ?

Answer 39

they have a 2+ charge - they become larger as we go down the group meaning the charge is spread out over a larger area so low charge density

Question 40

why is barium carbonate more stable than magnesium in the cloud in CO3 2- / NO3- ions ?

Answer 40

Mg 2+ is a smaller ion so it has a higher charge density and distorts the electron cloud more than Ba+ which has a lower charge density

Question 41

the less distortion the more / less stable the carbonate is ?

Answer 41

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