Group 1 and 2

Question 1

reason for Li and Mg to have a diagonal rel

Answer 1

from Li to Na; polarizing power decreases so Li+ has greater pol power. this is due to smaller size of Li
between Na and Mg, Mg2+ Has a greater pol pwoer bc it has a higher chagre and roughly the same size.
Li and Mg form compounds with a similar degree of polarising power and covalent character.

Question 2

explain the low 1st IE of group 1

Answer 2

group 1 elements are relatively large in size and the electron that needs to be removed is single and in an s orbital.

Question 3

explain why the 1st IE of group 1 is much lower than the 2nd IE

Answer 3

in the 1st IE the lectron is removed from an s orbital while in the 2nd IE the elexctron is removed from a noble gas core which is closer to the nucleus and hence requires more energy.

Question 4

what affects does the increase in size and increase in shielding on going down the group 1, have on group 1 elements

Answer 4

this allows the outermost electron to be lost with increasing ease. this results in increase in reactivity and electopositive character as the ram increases.

Question 5

how are group 1 metals stored?

Answer 5

under oil

Question 6

reason for group 1 metals to have colured flames

Answer 6

since the outermost electron is easily excited

Question 7

flame test of Li

Answer 7

red

Question 8

flame test of Na

Answer 8

bright yello

Question 9

flame test of potassium

Answer 9

lilac

Question 10

flame test of rubidium

Answer 10

red

Question 11

flame test of caesium

Answer 11

blue

Question 12

why does the melting point decrease on going down group 1

Answer 12

this is due to the large atomic size which leads to weaker forces between neighbouring atoms. thi sis because of the reduced attration of the nuclear charge for the shared mobile outer electrons as these e- get further away

Question 13

characteristics of group 1 salts

Answer 13

usually white unless anoin is coloured,,, all soluble in water

Question 14

structure of group 1 elements

Answer 14

body centered cubic structrue. cubic with an atom at the centre surrounded by 8 other atoms.

Question 15

group 1 reaction with wtaer

Answer 15

h2 and hydroxide

Question 16

reaction of group 1 elements withh O2; Li, Na, K, Rb and Cs

Answer 16

Li makes Li2O lithium monoixde
Na makes Na2O
in excess O2 Na produces Na2O2 (peroxide)
K, Rb and Cs react with O2 to produce superoxides of KO2, RbO2 and CsO2

Question 17

what makes a salt stable?

Answer 17

they become more stable upon increase of an ionic chare or decrease in ionic radius. these will make it easier to approach each other in the solid crystal

Question 18

examples to illustrate the diagonal relationship between Li and Mg

Answer 18

decomposition on heat of nitrates;
group 1; NaNO3 = NaNO2 and O2
Li and Mg: LiNO3 =Li2O + NO2 and O2

Question 19

thermal stability of group 1 nitrates

Answer 19

+O2;;; grp1 form peroxides and super oxides
Mg and Li give the oxide

heating carbonates- grp 1 stable, Li and Mg give oxide and CO2
heating hydroxide- grp 1 stable, Li and Mg give oxide and water
heating nitrateV- grp 1 give nitrite and O2, Li and Mg give oxide, NO2 and O2

grp 1 hydrogencarbonates can exist as solids, Li and Mg only exist in soution

Question 20

thermal stability of carbonates of group 1

Answer 20

thermally stable apart from Li which produces Li2O and CO2

Question 21

thermal stability of hydrogen carbonates of group 1

Answer 21

only group to form stable, and SOLID hydrogen carbonate compounds. apart from Li.
on heat; NaHCO3 = Na2CO3 + CO2 and H2O
Li prodcues the same products but LiHCO3 is only stble in solution

Question 22

stability fo hydroxides of group 1

Answer 22

stable apart from LiOH which produces Li2O and H2O

Question 23

reactions of group 1 oxides and peroxides with water

Answer 23

Na2O + H2O = NaOH

Na2O2 +H2O = NaOH +H2O2

Question 24

quality of group 1 hydroxies( excluding Li)

Answer 24

they are deliquescent- asorb water vapour from the air and issolve in it

Question 25

characteristic of hydrated sodium carbonate

Answer 25

effflorescent -loses water of of crystalliation without heating

Question 26

flame test of calcium

Answer 26

brick reed

Question 27

flame test of strontium

Answer 27

crimson

Question 28

flame test of barium

Answer 28

apple green

Question 29

is mp and bp of group 2 higher than those of group 1?

Answer 29

yes, due to 2 electrins being avalible for metallic bonding.

Question 30

solubility of group 1 compounds with refernce to hydration and lattice enthalpies

Answer 30

first there is the seperation of the ions. endothermic. the neergy supplied is equal to the lattice energy. the second step is hydration of the ions. exothermic. the energy released is the hydration energy. all common salts are solubel since the cations ar esinglky charged and energy required to break the lattice is low

Question 31

Is the first IE of group 2 higher than that of group 1?

Answer 31

yes, from group 1 to group 2, electrons are enterin gthe same shell so shielding remains the same. the nuclear charge and atomic radius are decreasing resulting in greater elecrostatic force of attraction between the nucleus on the outer electron.

Question 32

reaction of group 2 metals with water

Answer 32

they liberate H2 and the hydroixde. Be does not react with water and Mg reacts with steam to make MgO and H2

Question 33

reaction of group 2 with oxygen. mentions requiremnts for Mg and any specific info abt Ca

Answer 33

all react to form white solid monoxides. mg does not react with dry airat room temp, but pxides in damp air forming MgO which becomes teh hydroxide and then carbonate. on exposure to air Ca forms CaO, then Ca(OH)2 with water and CaCO3 with CO2

Question 34

what makes thermal stability? how does decomposing into different compounds help achieve stability?

Answer 34

the greater the charge and smaller the ion the more stable the compound as the ions will be able to approach closer to each other. large aninos decompose on heating to form smaller ions such as oxides,, the charge of 2- is spread over a smaller ion therefore the oxide would be more strongly attracted to the cation

Question 35

group 2 nitrate thermal stability

Answer 35

decompose to from oxide, NO2 and O2

Question 36

thermal stability of grou p2 carbonates

Answer 36

oxide and CO2

Question 37

thermal stability of group 2 hydrogen carbonates

Answer 37

only exist in solutions bc they are very unstable | decompose to corm carbonates, H2O and CO2

Question 38

thermal stability of grp 2 hydroxides

Answer 38

decompsoe to form oxide and water

Question 39

discuss lattice enthalpy and hydration enthalpy difference for small and large ion in the compound

Answer 39

small ion; highly endothermic lattice dissocation (hard to break up) and highly exothermic hydration. vice versa for large ions

Question 40

solubility of sulfates of grp 2

Answer 40

``` MgSO4 -soluble CaSO4- sparingly soluble SrSO4- insoluble BaSO4-insoluble down the grp; change in lattic disssocation is negligble due to large size of SO42-. cation size increases so decrease in enthalpy of hydration (difficult to attract water). on adding lattice diss and hydration ent, the value for enthalpy of solution becomes less exo therefore less soluble ```

Question 41

solubility of grp 2 hydroxies

Answer 41

OH- is a small ion and lattic ent is very significant. due to increase in cation size down the grp, lattice enth decreases. the rate at which lattic end becomes less endo is more than the rate at which ent of hydration becomes less exo so on going down the grp, solubility increases

Question 42

two ways of distinguishing between mg2+ and Ba2+

Answer 42

- add NaOH- Mg2+ forms a white ppt and Ba has no visible reaction - add H2SO4- no visible reactino with Mg2+, white ppt with Ba2+

Question 43

hardness of group 2 metals down the group

Answer 43

harndess decreases due to weakining of the metallic bond. the radisu is increasing therefore less attraction between the nuclei and delocalised electrons

Question 44

comment on the ionic/covalent character of the chlorides of Na, Mg and Al and if they can be hydrolysed

Answer 44

NaCl is ionic, MgCl2 is partially covalent and AlCl3 is found as a simple molecular compound(high degree of covalent character). NaCl ionizes, MgCl2 partially hydrolyses to form Mg(OH)Cl2 and AlCl3 undergoes complee hydrolysis

Question 45

why is MgO more stable than MgCO3? why are group 1 carbonate sstable

Answer 45

across a period the size of the cation decreases but the charge increases therefore Mg2+ has a higher polarizing power than Na+. the increases in polarising power, the greater the distortion of the e- cloud of the anion, causing MgCO3 to decoposse to MgO and CO2. O2_ is a small ion with a high charge and it is not easily polarisbale making MgO stable.

Question 46

stability of carbonates down group 2

Answer 46

stability increases as the size of te cation increases causing less distortion of the e-cloud of the carbonate anion due to smaller polarising power.

Question 47

how to make Mg(OH)2

Answer 47

react Mg with NaOH