SC6: groups in the periodic table

Question 1

what are group 1 elements called?

Answer 1

alkali metals

Question 2

physical properties of alkali metals

Answer 2

-shiny
-soft (can be cut with a knife)
-low melting points
-low density (some can float on water)

Question 3

melting points _____ as you go down the alkali metals

Answer 3

decrease

Question 4

reactivity _____ as you go down the alkali metals

Answer 4

increases

Question 5

why do all the alkali metals have similar chemical properties

Answer 5

atoms of group 1 elements all have one electron in their outer shell

Question 6

what do the alkali metals react with water to produce?

Answer 6

a metal hydroxide and hydrogen

Question 7

lithium and water

Answer 7

fizzes steadily, slowly becomes smaller until it disappears

Question 8

sodium and water

Answer 8

melts to form a ball, fizzes rapidly, quickly becomes smaller until it disappears

Question 9

potassium and water

Answer 9

quickly melts to form a ball, burns violently with sparks and a lilac flame, disappears rapidly, often with a small explosion

Question 10

what happens when a group one element takes part in a reaction

Answer 10

its atoms lose their outer electron and form cations

Question 11

what do cations have to do with the reactivity of group 1 metals?

Answer 11

the more easily cations form, the more reactive the metal

Question 12

why does reactivity of group 1 metals increase as you go down the group

Answer 12

-the atoms become larger
-the outer electron becomes further from the nucleus
-the force of attraction between the nucleus and the outer electron decreases
-the outer electron is lost more easily

Question 13

what are halogens?

Answer 13

-simple molecules
-each molecule contains two halogen atoms joined by a single covalent bond

Question 14

the colour and physical states of chlorine, bromine and iodine at room temperature:

Answer 14

chlorine:
pale green gas

bromine:
brown liquid

iodine:
purple-black solid

Question 15

melting and boiling points _______ going down group 7

Answer 15

increase

Question 16

why do the melting points and boiling points of the halogens increase going down group 7

Answer 16

-the molecules become larger
-the intermolecular forces become stronger
-more energy is needed to overcome these forces

Question 17

why do halogens all have similar chemical properties?

Answer 17

they all have seven electrons on their outer shells

Question 18

halogen + metal

Answer 18

salt

Question 19

halogens become _____ reactive going down group 7

Answer 19

less

Question 20

reactions with fluorine and iron wool (+colour)

Answer 20

cold iron wool burns to produce white iron(III) fluoride

Question 21

reactions with chlorine and iron wool (+colour)

Answer 21

hot iron wool burns vigorously to produce orange-brown iron(III) chloride

Question 22

reactions with bromine and iron wool (+colour)

Answer 22

hot iron wool burns quickly to produce red-brown iron(III) bromide

Question 23

reactions with iodine and iron wool (+colour)

Answer 23

hot iron wool reacts slowly in iodine vapour to produce grey iron(II) iodide

Question 24

hydrogen + halogen

Answer 24

hydrogen halide

Question 25

what are hydrogen halides at room temperature?

Answer 25

gases

Question 26

what do hydrogen halides produce when they dissolve in water?

Answer 26

acidic solutions

Question 27

fluorine’s reaction with hydrogen

Answer 27

explodes in the cold and dark, forming hydrogen fluoride

Question 28

chloride’s reaction with hydrogen

Answer 28

explodes with a flame in sunlight, forming hydrogen chloride

Question 29

bromine’s reaction with hydrogen

Answer 29

vigorous reaction with burning hydrogen, forming hydrogen bromide

Question 30

iodine’s reaction with hydrogen

Answer 30

very slow reaction when heated strongly, forming some hydrogen iodide

Question 31

test for chlorine

Answer 31

-damp litmus paper is bleached white when it is placed in chlorine
-if damp blue litmus paper is used, the paper turns red then white

Question 32

why are halogens less reactive as you go down the group?

Answer 32

-with group 7 elements, an electron must be gained
-electrons are attracted to the nucleus, therefore if there is a short distance between the outer shell and the nucleus, electrons will have a stronger attraction to the nucleus
-as you go down the group, shells increase and it is harder for the nuclei to attract electrons

Question 33

halogen displacement reaction

Answer 33

a more reactive halogen can displace a less reactive halogen from solutions of its salts

Question 34

boiling points of noble gases

Answer 34

-low
-increase as you go down the group

Question 35

why do boiling points of noble gases increase as you go down the group?

Answer 35

-the atoms become larger
-the intermolecular forces between the atoms become stronger
more energy is needed to overcome these forces

Question 36

densities of noble gases

Answer 36

-particles in gases are widely spaced, so the noble gases have low densities
-density increases going down the group

Question 37

are the noble gases reactive?

Answer 37

no, they’re inert

Question 38

why are noble gases inert?

Answer 38

-when elements react, their atoms complete their outer shells by losing, gaining, or sharing electrons
-the atoms of noble gases already have complete outer shells, so they have no tendency to lose, gain, or share electrons

Question 39

helium

Answer 39

-used as a lifting gas in party balloons and airships

helium is:
-less dense than air, so balloons and airships rise
-non-flammable so the helium cannot set on fire

Question 40

argon

Answer 40

-used as a ‘shield gas’ when welding pieces of metal together

argon is:
-denser than air, so it stops air getting to the metal
-inert, so the hot metal cannot oxidise and spoil the weld

Question 41

why are noble gases used in filament lamps? (lamps that become very hot and glow brightly when an electric current is passed through them)

Answer 41

-the hot metal wires will burn away if any oxygen from air is present in the lamp
-argon, krypton and xenon are very unreactive
-they replace the air inside the lamp, preventing the metal wire from burning away