period 3

Question 1

physical properties of period 3

Answer 1

atomic radius decreases down the period
electronegativity increases along the period
1st ionisation energy increases along the the period
(increase in nuclear charge , same amount of shielding)

Question 2

anomalies in period 3

Answer 2

al has a lower IE than mg
mg has a 3s electron removed but al has a 3p electron removed
3p is higher in energy than 3s

s has a lower IE than P
p has a 3p electron removed which is unpaired
s has a 3p electron removed which is paired
s has lower ie due to electron pair repulsion

Question 3

reactions of period 3 with water

Answer 3

undergo redox

Question 4

sodium with water

Answer 4

2NA(s) + 2H20(l) -> 2NaOH(aq) +H2(g)
vigorous reaction
metal fizzes rapidly and melts due to the heat released
strong alkaline formed

Question 5

magnesium with water and steam

Answer 5

water
Mg(s) + 2H20(l)->Mg(OH)2(aq) + H2(g)
slow reaction only a few bubbles of gas
weak alkali solution as mg(oh)2 is sparingly soluble

steam
Mg(s) + H2O(g) -> MgO(s) + H2(g)
faster reaction as higher temp needed to generate the steam

Question 6

chlorine with water

Answer 6

Cl2(g) + H2O(l) -> HClO(aq) + HCl(aq)
in bright sunlight
2Cl2(g) + 2H2O(l) -> 4HCl(aq) + O2(g)

Question 7

chemistry of period 3 oxides

Answer 7

oxides of na, mg , and al are all ionic
silicon dioxide is macromolecular
oxides of p and s are simple molecules

Question 8

basic oxides

Answer 8

group 1+2 - alkali
Na2O(s) + H2O(l) -> 2NaOH(aq)
MgO(s) + H2O(l) ->Mg(OH)2(aq)
mg(oh)2 sparingly soluble so weakly alkaline

Question 9

insoluble oxides

Answer 9

aluminium oxide and silicon dioxide are both insoluble in water
undergo no reaction
ph is 7

Question 10

acidic oxides

Answer 10

oxides of the non metals are acidic
P4O10(s) + 6H2O(l) -> 4H3PO4(aq)
strong triprotic acid and fully dissociates

SO2(g0 + H2O(l) -> H2SO3(aq)
dissolves fairly well to give a slightly weaker acid

SO3(g) + H2O(l) -> H2SO4(aq)
reacts violently with water to give stron gacid that fully dissociates

Question 11

acid/base nature of the p3 oxides

Answer 11

across the period the oxides change from being basic to neutral to acidic

Question 12

basic oxides reacting

Answer 12

react with acids to produce a salt and water
Na2O(s) + H2SO4(aq) -> Na2SO4(aq) + H2O(l)
MgO(s) + 2HCl(aq) -> MgCl2(aq) + H2O(l)

Question 13

amphoteric oxides reacting

Answer 13

can act as an acid or a base so can react with an acid or a base
acts as a base reacts with an acid :
Al2O3(s) +6HCl(aq) -> 2AlCL3(aq) + 3H2O(l)
acts as an acid reacts with a base :
Al2O3(s) + 2NaOH(aq) + 3H2O(l) -> 2NaAl(OH)4(aq)

Question 14

acidic oxides reacting

Answer 14

react with bases
starting from oxide -P4O10 + 12NaOH -> 4Na3PO4(aq) + 6H2O
from phosphoric acid -
H3PO4(aq) + 3NaOH(aq) -> Na3PO4(aq) + 3H2O(l)

SO2(aq) + 2NaOH(aq) -> Na2SO3(aq) + H2O(l)

Question 15

very rarely why is silicon oxide is classified as an acidic oxide

Answer 15

SiO2 neutralises bases
SiO2 + 2NaOH -> Na2SiO3 + H2O

Question 16

Sodium with oxygen

Answer 16

2Na(s) + 1/2O2(g) -> na2o(s)
Burns brightly in o2 gas with yellow flame to form a white solid

Question 17

Magnesium with o2

Answer 17

2mg (s) + o2(g) -> 2mgo(s)
Burns brightly in o2 with white flame to form a white solid

Question 18

Aluminium with o2

Answer 18

4al(s) + 3o2(g) -> 2al2o3(s)
Burns with white flame

Question 19

Silicon with o2

Answer 19

Si(s) + o2(g) -> sio2(s)

Question 20

Phosphorous with o2

Answer 20

P4(s) + 5o2(g) -> p4o10(s)
White fumes and no ppt
White p gives white flame

Question 21

Sulfur with o2

Answer 21

S(s) + o2(g) -> so2(g)
Pale blue flame and colourless gas