3.2.2 Group 2, the alkaline earth metals

Question 1

what are group 2 elements also known as

Answer 1

the alkaline earth metals

Question 2

trend in atomic radius down group 2

Answer 2

as you go down a group in the periodic table, the atomic radius gets larger

Question 3

explanation for trend in atomic radius down group 2

Answer 3

extra electron shells are added as you go down the group

Question 4

how many electrons do group 2 elements have in their outer shell

Answer 4

2

Question 5

what ions do group 2 elements form

Answer 5

2+ ions

Question 6

trend in ionisation energy down group 2

Answer 6

first ionisation energy decreases down the group

Question 7

explanation for trend in ionisation energy down group 2

Answer 7

as you go down group 2 atomic radius increases (due to more electron shells). the outer electrons are also shielded from nuclear pull by the extra electron shells. this means the electrostatic attraction between the nucleus and the outer electron is wweaker so less energy is need to remove an electron

Question 8

what do group 2 elements do when they react

Answer 8

they lose electrons to form positive ions

Question 9

what does reactivity mean in terms of electrons

Answer 9

the easier it is to lose electrons, the more reactive the element

Question 10

trend in reactivity down group 2

Answer 10

reactivity increases down group 2

Question 11

general trend in melting point down group 2

Answer 11

melting point decreases down group 2

Question 12

what is the anomaly in the melting point trend down group 2

Answer 12

magnesium is the anomaly

Question 13

why is magnesium an anomaly (melting point)

Answer 13

as the crystal structure (arrangement of the metallic ions) changes

Question 14

explanation for general trend in melting point down group 2

Answer 14

going down the group the metal ions get bigger but the number of delocalised electrons per atom (2) and the charge on the ion (2+) doesn’t change. the larger the ionic radius, the further away the delocalised electrons are from the positive nuclei so it takes less energy to break the bonds

Question 14

group 2 elements structure

Answer 14

typical metallic structure with positive ions in a crystal structure surrounded by delocalised electrons from the outer electron shells

Question 15

when group 2 elements react are they reduced or oxidised

Answer 15

oxidised from a state of 0 to +2

Question 16

reaction between water and beryllium

Answer 16

doesn’t react

Question 17

reaction between water and magnesium

Answer 17

insignificant reaction, very slow

Question 18

reaction between water and calcium

Answer 18

steady reaction, Ca(OH)2 (some white precipitate) and colourless H2 gas

Question 19

reaction between water and strontium

Answer 19

fairly quick, alkaline colourless Sr(OH)2 solution and colourless H2 gas

Question 20

reaction between water and barium

Answer 20

rapid, alkaline colourless Ba(OH)2 solution and colourless H2

Question 21

reaction between steam and magnesium

Answer 21

burns vigorously, white MgO solid and colourless H2 gas

Question 22

reaction between steam and calcium

Answer 22

burns very vigorously, white CaO solid and colourless H2 gas

Question 23

reaction between steam and strontium

Answer 23

burns explosively, white SrO solid and colourless H2 gas

Question 24

reaction between steam and barium

Answer 24

burns explosively, white BaO solid and colourless H2 gas

Question 25

why do the reactions with water become quicker down group 2

Answer 25

elements react more readily down the group as the ionisation energies decrease

Question 26

what does the solubility of group 2 compounds depend on

Answer 26

the anion in the compound

Question 27

trend in solubility of group 2 hydroxides down the group

Answer 27

become more soluble as you go down the group

Question 28

trend in solubility of group 2 sulfates down the group

Answer 28

become less soluble as you go down the group

Question 29

hydroxide ion

Answer 29

OH-

Question 30

sulfate ion

Answer 30

(SO4)2-

Question 31

is barium sulfate soluble or insoluble

Answer 31

insoluble

Question 32

what is barium sulfate used in

Answer 32

can be used in medicine

Question 33

what do X-rays usually look at

Answer 33

bones

Question 34

what don't X-rays pass through

Answer 34

soft tissues e.g. the digestive system

Question 35

barium sulfate and X-rays

Answer 35

barium sulfate is opaque to X-rays (they won't pass through it)

Question 36

how is barium sulfate used in medicine

Answer 36

barium sulfate is used in barium meals to help diagnose problems with the oesophagus, stomach or intestines

Question 37

how is the barium meal given to the patient

Answer 37

a patient swallows the barium meal which is a suspension of barium sulfate

Question 38

explanation for how is barium sulfate used in medicine

Answer 38

barium sulfate coats the tissues, making them show up on the X-rays, showing the structure of the organs

Question 39

why can't other barium compounds be used for barium meals

Answer 39

solutions containing barium ions are poisonous but barium sulfate is insoluble so forms a suspension rather than a solution

Question 40

what is a use of magnesium

Answer 40

magnesium is used as part of the process of extracting titanium from its ore

Question 41

first step of extracting titanium from its ore

Answer 41

the main titanium ore, titanium(IV) oxide (TiO2) is first converted to titanium(IV) chloride (TiCl4) by heating it with carbon in a stream of chlorine gas

Question 42

second step of extracting titanium from its ore

Answer 42

titanium chloride is then purified by fractional distillation, before being reduced by magnesium in a furnace at almost 1000 degrees C

Question 43

equation for using Mg to extract titanium from its ore

Answer 43

TiCl4( g) + 2Mg( l) = Ti (s) + 2MgCl2 (l)

Question 44

what can burning fossil fuels produce

Answer 44

sulfur dioxide

Question 45

can sulfur dioxide be removed from flue gases

Answer 45

acidic sulfur dioxide can be removed from flue gases by reacting with an alkali (wet scrubbing)

Question 46

what two compounds can be used to remove SO2 from flue gases

Answer 46

calcium oxide (lime) = CaO calcium carbonate (limestone) = CaCO3

Question 47

removing SO2 from flue gases step 1

Answer 47

slurry is made by mixing either calcium oxide or calcium carbonate with water

Question 48

removing SO2 from flue gases step 2

Answer 48

slurry is then sprayed onto the flue gases

Question 49

removing SO2 from flue gases step 3

Answer 49

sulfur dioxide reacts with the alkaline slurry and produces a solid waste product, calcium sulfite

Question 50

equation for removing SO2 from flue gases using CaO

Answer 50

CaO (s) + 2H2O (l) + SO2 (g) = CaSO3 (s) + 2H2O (l)

Question 51

equation for removing SO2 from flue gases using CaCO3

Answer 51

CaCO3 (s) + 2H2O (l) + SO2 (g) = CaSO3 (s) + 2H2O (l) + CO2(g)

Question 52

calcium hydroxide name/formula

Answer 52

- called slaked lime - Ca(OH)2

Question 53

calcium hydroxide use

Answer 53

used in agriculture to neutralise acidic soils

Question 54

magnesium hydroxide formula

Answer 54

Mg(OH)2

Question 55

magnesium hydroxide use

Answer 55

used in some indigestion tablets as an antiacid (neutralises excess stomach acid)