Topic 6 - Groups in the periodic table

Question 1

GROUP 1 - Explain why some elements can be classified as group 1 metals

Answer 1

GROUP 1 - ALKALI METALS

Same physical properties:

• good heat and electricity conductors
• shiny when freshly cut
• soft
• relatively low melting points (but solid)

Question 2

GROUP 1 - explain what happens when a group 1 metal reacts with water

Answer 2

Produces an alkaline metal hydroxide & hydrogen

Eg:
Sodium + water —> sodium hydroxide + hydrogen

Question 3

GROUP 1 - describe the reactivity of the alkali metals

Answer 3

REACTIVITY increases down the group:

LITHIUM - fizzes steadily
SODIUM - melts into a ball from heat released and fizzes rapidly
POTASSIUM - gives off sparks, hydrogen produced burns with a lilac-coloured flame

Question 4

GROUP 1 - Explain the density and storage of the few metals

Answer 4

DENSITY:
Lithium, sodium, potassium less dense than water - float

STORAGE:
Lithium, sodium, potassium stored in oil - keeps air + water away

Question 5

GROUP 1 - explain the pattern of reactivity in terms of electronic configuration

Answer 5

all have one electron in outer shell, this lost to form ions with +1 charge

easier outer electron is lost, more reactive metal

Question 6

GROUP 7 - what are the colours and states of chlorine, bromine and iodine at room temp

Answer 6

CHLORINE - yellow/green gas

BROMINE - red/brown liquid

IODINE - dark grey (forms purple vapour when warmed) solid

Question 7

GROUP 7 - describe the melting and boiling points as you go down

Answer 7

MELTING POINTS increase

BOILING POINTS increase

Question 8

GROUP 7 - describe the bonding in simple molecular substances

Answer 8

when simple molecular substances melt or boil:

• weak intermolecular forces are overcome
• strong covalent bonds dont break

Question 9

GROUP 7 - describe the bonding as you go down the group

Answer 9

• intermolecular forces between molecules stronger

- more heat energy needed to overcome forces

Question 10

GROUP 7 - describe the test for chlorine

Answer 10

put damp blue litmus paper into container. if chlorine present then paper turns red, then is bleached white

Question 11

GROUP 7 - what is formed when the halogens react with metals

Answer 11

halogens + metals = metal halide compounds

eg // sodium + chlorine —> sodium chloride

Question 12

GROUP 7 - explain what happens in terms of ions when halogens react with metals

Answer 12

halogen atoms GAIN electrons and are REDUCED

ions formed:

• have 1- charge
• are called halide ions

HALIDES are compounds of metals/hydrogens with halogens

Question 13

GROUP 7 - explain the electronic configuration going down the group

Answer 13

going down:

• outer shell gets further from nucleus
• • shielding by inner electrons
• force of attraction between nucleus and outer shell electrons gets weaker
• electrons gained less easily
• elements become less reactive

Question 14

GROUP 7 - explain how the electronic configuration changes when a halogen reacts with a metal/hydrogen

Answer 14

halogen atom - 7 electrons

when reacts, each halogen gains one electron to complete outer shell

less easily halogen gains electron, less reactive halogen is

Question 15

GROUP 7 - explain what happens in a halogen displacement reaction (using chlorine and bromine as an example)

Answer 15

these are REDOX reactions eg when chlorine displaces bromine from bromide ions in solution

1. chlorine atoms gain electrons and reduced to chloride atoms:
   Cl2 (aq) + 2e- —> 2Cl- (aq)
2. bromide ions lose electrons and are oxidised to bromine:

2Br- (aq) —> Br2(aq) + 2e-

Question 16

GROUP 7 - explain how you can demonstrate halogen displacement reactions

Answer 16

adding a HALOGEN solution to a METAL HALIDE solution, see if mixture darkens eg:

‘chlorine water’ displaces bromine from aqueous sodium bromide solution

Cl2 (aq) + 2NaBr(aq) —> 2NaCl (aq) + Br2 (aq)

Question 17

GROUP 7 - explain how fluorine, chlorine and bromine react with hydrogen

Answer 17

FLUORINE - reacts explosively in dark

CHLORINE - reacts explosively in sunlight

BROMINE - reacts vigorously in a flame

Question 18

GROUP 7 - explain how the hydrogen halides react with water

Answer 18

all dissolve in water, producing ACIDIC solutions

eg// hydrogen chloride gas HCl (g) produces hydrochloric acid HCl (aq), fully dissociates to form H+ (aq) and Cl- (aq) ions

Question 19

GROUP 7 - using the reactivity of bromine, iodine and chlorine predict whether astatine will react with potassium iodide

Answer 19

astatine will not react with potassium iodide because:

• reactivity decreases down group 7 (astatine at bottom)
• astatine less reactive than iodine

Question 20

GROUP 7 - describe which halogens displace each other when reacted with the potassium halides (chlorine, bromine, iodine reacting with chlorine, bromine, iodine)

Answer 20

1. chlorine with bromide
2. chlorine with iodide
3. bromine with iodide

they all turn darker, showing a displacement reaction

Question 21

GROUP 0 - explain why the noble gases are chemically inert

Answer 21

lack of reactivity because:

• atoms have full outer shells so
• no tendency to lose or gain electrons

Question 22

GROUP 0 - explain the use of helium and properties needed

Answer 22

USE - lifting gas in party balloons and airships

NEEDS low density & inertness

REASONS - less dense than air so balloons and airships rise, non flammable

Question 23

GROUP 0 - explain the use of argon, krypton and xenon and properties needed

Answer 23

USE - filling gas in filament lamps

NEEDS inertness

REASONS - metal filament becomes hot enough to glow, inert gases stop it burning away

Question 24

GROUP 0 - explain the use of argon and properties needed

Answer 24

USE - shield gas during welding

NEEDS inertness

REASONS - denser than air, keeps air away from metal, inert so metal doesnt oxidise

Question 25

GROUP 0 - describe the trend in densities and boiling points as you go down the group

Answer 25

densities increase as you go down the group

boiling points get higher as you go down

Question 26

why does oxygen gas have an extremely low boiling point

Answer 26

weak intermolecular forces