periodicity (chapter 7) and reactivity trend (chapter 8 ) (model exam answers)

Question 1

(Textbook) explain in terms of first ionisatin energy why the the reactivity increases down group 2 ( 4)

Answer 1

Down a group, electrons are added to a new shell, further from the nucleus

There are more inner shells between the outer electrons and the nucleus,

increasing the shielding Attraction between nucleus and outer electrons decreases

Therefore less energy is required to lose an electron and reactivity of Group 2 increases

Question 2

define disproportionation

Answer 2

Disproportionation is the simultaneous oxidation and reduction of the same element in the same redox reaction

Question 3

why is second ionsiation energy important when explaining group 2 reactivity

Answer 3

Group 2 elements react by losing two electrons to form 2+ ions (EXPLAIN EVERYTHING )

Question 4

show the metallic bonding by using a diagram (3 )

Answer 4

1 mark for showing a regular arrangement of labelled 2+ ions

1 mark for showing delocalised electrons

High melting point as the strong attraction between positive ions and delocalised requires a large quantity of energy to be overcome

NOTE; MUST INCOUDE ATLEAST 2 DELOCALISED ELECTRON PER ROW

Question 5

Careless mistake reaction of barium with water

Answer 5

Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)

Ba (OH)2 not Ba (OH) (CHECK THE CHARGES !)

Question 6

How else can conuctivity be induced

Answer 6

OH- ions

Question 7

observations when looking at the reaciton of carbonates (2 )

Answer 7

fizzing and solid dissolves

Question 8

WHEN DRAWING BONDING —–> THINK ABOUT WHETHER ITS COVALENT OR IONIC

eg draw bondign in SrCL2

Answer 8

Question 11

explain why chlroine is more reactive than bromne (1)

Answer 11

. chlroine gains an electron more easily than bromine (1)

.since chlorine is a smaller atom than bromine (1)

.therefore there is less shielding effect caused by the electrons in chlorine than bromine (1) due to fewer shells between nucleus and electrons in bromine (1)

.in chlorine atom, nuclear attraction to electron to be gained is greater than bromine (1)