Topic 9 - Groups Of The Periodic Table

Question 1

Inert

Answer 1

The noble gasses have full outer shell so are unreactive.

Question 2

Main properties of noble gasses.

Answer 2

1) Low boiling points
2) Monatomic (full outer shell)
3) Low densities
4) Inert, not flammable

Question 3

Helium
Use and why

Answer 3

Used as a lifting gas in party balloons and airships.

Less dense than air, so balloons and airships rise.
Non-flammable so the helium cannot set on fire.

Question 4

Argon
Use and why

Answer 4

Used instead of air in lightbulbs.

Inert stops the metal filament from reacting with oxygen and burning out the metal filament

Question 5

Neon
Use and why

Answer 5

Red neon signs, lasers

Conductor of electricity at high voltage and gives out red light.

Question 6

Krypton
Use and why

Answer 6

Used in photography flash bulbs.

Produces very white light.
Stops the flash filament from burning up during the high temperature flashes.

Question 7

What else can helium and argon be used for?

Answer 7

Welding
Inert so stops hot metals reacting with oxygen - reduces brittle oxide formation reducing the weld quality.

Question 8

Why are the alkali metals in group 1?

Answer 8

They all have 1 electron in their outer shell.

Question 9

What happens to reactivity as you go down group 1?

Answer 9

Elements get more reactive.
The more shells an atom has, the further the outer shell electron is from the nucleus. This decreases the attraction between the nucleus and the outer shell electron. This makes it easier to remove the outer shell electron and so the more reactive the alkali metal is.

Question 10

What is the word equation for alkali metal reactions with water?

Answer 10

Alkali metal + water —> Metal hydroxide + Hydrogen

Example
Lithium + water —> Lithium hydroxide + hydrogen
Alkaline Bubbles
2Li + 2H2O —> 2LiOH + H2

Question 11

Properties of alkali metals?

Answer 11

• Low melting and boiling point
• Soft
• Low density
• Shiny when cut but goes dull quickly

Question 12

Lithium physical properties

Answer 12

• Grey
• Soft
• Shiny but goes dull when cut

Question 13

Lithium reaction with water

Answer 13

Move around the surface fizzing furiously.

Question 14

Lithium colour and Ph of solution

Answer 14

• Blue
• 13-14

Question 15

Sodium physical properties

Answer 15

• Lighter grey
• Softer
• Goes dull quickly when cut

Question 16

Sodium reaction with water

Answer 16

Float around the surface, fizzing furiously.
Melt in the heat of the reaction.

Question 17

Sodium colour and PH of solution

Answer 17

• Dark blue
• 13-14

Question 18

Potassium physical properties

Answer 18

• Really soft
• Light grey

Question 19

Potassium reaction with water

Answer 19

Floats around the surface fizzing furiously
Melt in heat of reaction
Lilac flame gets hit enough to ignite the hydrogen gas being produced.

Question 20

Potassium colour and PH of solution

Answer 20

• Dark blue
• 14

Question 21

Fluorine
State and colour at room temperature

Answer 21

Pale yellow gas.

Question 22

Chlorine
State and colour at room temperature

Answer 22

Pale green gas

Question 23

Bromine
State and colour at room temperature

Answer 23

Red/orange liquid

Question 24

Iodine
State and colour at room temperature

Answer 24

Grey solid

Question 25

Astatine
State and colour at room temperature

Answer 25

Black solid

Question 26

What happens to reactivity going down group 7?

Answer 26

The halogens become less reactive

When an element in group 7 takes part in a reaction, its atoms outer shells gain an electron and form negatively charged ions, called anions. The less easily these anions form, the less reactive the halogen.

• The atoms become larger.
• The outer shell becomes further from the nucleus
• The force of attraction between the nucleus and the outer shell decrease
• An outer electron is gained less easily
• The halogen becomes less reactive

Question 27

What happens to the melting and boiling point down group 7?

Answer 27

They increase because going down group 7 the molecules become larger, the intermolecular forces become stronger.

Question 28

What do the group 7 molecules consist of and what does it mean?

Answer 28

Diatomic molecules, they contain 2 atoms that are chemically bonded.

Question 29

How to test for chlorine gas?

Answer 29

Damp blue litmus paper goes red then bleaches white.

Question 30

Halogens reaction with metal
Lithium + Chlorine

Answer 30

Lithium Chloride
2Li + Cl2 —> LiCl

Question 31

Halogens reaction with hydrogen
Hydrogen and fluorine

Answer 31

Hydrogen fluoride
H2 + 2F —> 2HF

Question 32

How does the colour of the halogens change as you go down the group?

Answer 32

They become darker.

Question 33

What do halogens have in common?

Answer 33

• They are fairly toxic
• Have low melting points
• All form acids when combined with hydrogen

Question 34

Displacement reactions

Answer 34

A displacement reactions happens when a more reactive element displaces the less reactive element from it compound.

Chlorine + potassium bromide —> Bromine + potassium chloride
Cl2 + 2KBr —> Br2 + 2KCl
The chlorine is reduced to chloride ions so the salt solution becomes potassium chloride. The bro Jed ions are oxidised to bromine, which turns the solution orange.

Question 35

What type of reactions are halogen displacement reactions?

Answer 35

Redox reactions. The halogens gain electrons (reduction) whilst halide ions loose electrons (Oxidation).

Question 36

What colour are the halide salt solutions?

Answer 36

Colourless

Question 37

What controls the colour of the product?

Answer 37

The less reactive halogen.

Question 38

Core practical: reactivity trends method

Answer 38

1) Start by measuring out a small amount of halide solution to each dot on your laminated sheet.
2) Add a few drops of halogen solution to it.
3) If you see a colour change then, then a reaction has happened - the halogen has displaced the halide ions from the salt. If no reaction happens, there wont be a colour change - the halogen is less reactive than the halide and so can’t displace it.

Question 39

Chlorine water colour

Answer 39

Pale yellow-green to colourless

Question 40

Bromine water colour

Answer 40

Orange

Question 41

Iodine water colour

Answer 41

Brown

Question 42

Chlorine water + bromide solution
Reaction colour

Answer 42

Orange solution (Br2)

Question 43

Chlorine water + potassium iodide
Reaction colour

Answer 43

Brown solution (I2)

Question 44

Bromine water + potassium iodide
Reaction colour

Answer 44

Brown solution (I2)

Question 45

What are spectator ions?

Answer 45

Ions that don’t change in a reaction.