Topic 8 - Periodic table

Question 1

what are the three groups we need to know in the periodic table?

Answer 1

• alkali metals
• halogens
• noble gas

Question 2

what group are alkali metals in ? what are the first 3 alkali metals ?

Answer 2

• they are the elements in group 1
• Lithium ( Li ) , Sodium ( Na ) , Potassium ( K )

Question 3

properties of alkali metals

Answer 3

• silvery solids that have to be stored in oil
• very soft : cut with knife
• have low MP and BP compared to other metals
• they all form 1+ ions and lose their valence electron to form ionic compounds

Question 4

reactivity trend of alkali metals

Answer 4

• as you go DOWN group 1, the reactivity of the metal INCREASES

Question 5

why do the alkali metals have this trend?

Answer 5

• increased atomic radius
• means increased distance between valence electron and positively charged nucleus
• weakens the attractive electrostatic force
• valence electron is removed more readily which makes it more reactive

Question 6

alkali metal + water

Answer 6

metal hydroxide + hydrogen

Question 7

metal hydroxide solutions

Answer 7

the hydroxides that are formed dissolve in water to give alkaline solutions and turn u.i purple

Question 8

reaction of alkali metals with water

Answer 8

the reaction becomes more violent and vigorous as you go down the group

Question 9

what group are halogens in ? what are the first 3 halogens ?

Answer 9

• they are elements in group 7
• Chlorine ( Cl ) , Bromine ( Br ) , Iodine ( I )

Question 10

properties of halogens

Answer 10

• they all exist as diatomic molecules and share 1 pair of electrons through covalent bonding

Question 11

what does chlorine look like at r.t

Answer 11

poisonous , green gas

Question 12

what does bromine look like at r.t

Answer 12

poisonous , red-brown liquid

Question 13

what does iodine look like at r.t

Answer 13

poisonous , dark-grey solid
gives off purple vapour when heated

Question 14

physical properties of halogens

Answer 14

as you go DOWN the group
- melting point INCREASES
- colours of halogens becomes DARKER

Question 15

test for chlorine

Answer 15

• use damp blue litmus paper
• it will turn from blue to white

Question 16

reactivity trend of halogens

Answer 16

• as you go DOWN group 7, the reactivity of the metal DECREASES

Question 17

why do the halogens have this trend?

Answer 17

• increased atomic radius
• means increased distance between valence electron and positively charged nucleus
• weakens the attractive electrostatic force
• becomes harder to attract an extra electron

Question 18

halogen + metal

Answer 18

metal halide ( sodium chloride )

Question 19

halogen + hydrogen

Answer 19

hydrogen halide

Question 20

hydrogen halides?

Answer 20

they dissolve in water to form acidic solutions

Question 21

displacement reactions involving halides

Answer 21

a more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt

Question 22

redox reactions

Answer 22

• both reduction and oxidation happen simultaneously
• halogens are reduced ( gain electrons ) to form halide ions
• the halide ions are oxidised ( lose electrons ) to form halides

Question 23

what group are noble gases in ? what are the first 3 noble gases ?

Answer 23

• they are in group 0
• Helium ( He ) , Neon ( Ne ) , Argon
  ( Ar )

Question 24

electronic configuration of noble gase

Answer 24

• they all have full outer shell of electrons

Question 25

why are noble gases inert / unreactive

Answer 25

• the outer shell is energetically stable
• they don’t need to give up or gain electrons to become more stable
• this means they don’t have to react with other substances
• they are also non flammable

Question 26

properties of all noble gases

Answer 26

all colourless, monoatomic gases at r.t

Question 27

why is inertness useful for a noble gas

Answer 27

for example argon provides an inert atmosphere in filament lamps as it is non-flammable

Question 28

why is the density of noble gases useful?

Answer 28

• noble gases have low densities
• helium and neon are less dense than air so can be pumped into balloons to make them float