Topic 6 - Groups in the Periodic table

Question 1

Describe uses of noble gases (5)

Answer 1

Helium - Party balloons, airships - low density than air, helps to float
Neon - Red neon signs, lasers.
Argon - Shielding gas in arc welding - creates inert atmosphere to stop oxygen from reacting with the hot metal
Xenon - Lights, lasers.
Krypton - Lights, Photographic flashguns - stops the flash filament from from burning up during high temperature flashes

Question 2

What would happen if you added bromine water (orange) to:

a) Potassium chloride
b) Potassium bromide
c) Potassium iodide

Answer 2

a) no reaction
b) no reaction
c) brown solution - I2 formed

Question 3

What do halogens exist as?

Answer 3

They exist as diatomic molecules (Cl2, Br2, I2, etc). They share one pair of electrons in a covalent bond to give both atoms a full outer shell.

Question 4

Give examples of metallic bonding

Answer 4

Copper, Lead, Iron, Titanium

Question 5

Describe the reactivity of alkali metals.

Answer 5

• Needs to lose one electron to get a full outer shell,
• Reactivity increases as you go down group 1 as the distance between the nucleus and the outer electron increases making the force weaker. The outer electrons is more easily lost as it further from the nucleus - so it’s less strongly attracted to the nucleus and less energy is needed to remove it; essentially it is willing to react with more things to get a full outer shell.

Question 6

What would happen if you added chlorine water (colourless) to:

a) Potassium chloride
b) Potassium bromide
c) Potassium iodide

Answer 6

a) no reaction
b) orange solution - Br2 formed
c) brown solution- I2 formed

Question 7

Describe the reactivity of noble gases

Answer 7

They are inert (nonreactive) because they have full outer shells.

Question 8

What is the symbol equation of the reaction of potassium with water?

Answer 8

2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)

Question 9

Describe the test for chlorine

Answer 9

You can test to see if a gas is is chlorine by holding a piece of damp litmus paper over it. Chlorine will bleach the litmus paper, turning it white. However, it may turn red at first as a solution is slightly acidic.

Question 10

How are hydrogen halides formed?

Answer 10

Halogen + Hydrogen ——> hydrogen halide

They can dissolve in water to form acidic solution

hydrogen + chlorine ——> Hydrogen chloride

hydrogen chloride + water ——> Hydrochloric acid

Question 11

Describe the reaction of potassium with water.

Answer 11

When potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame. There is sometimes a small explosion at the end of the reaction.

Question 12

What do the Halogen displacement reactions show?

Answer 12

Chlorine displaces both bromine and iodine from salt solutions. Bromine can’t displace chlorine, but it does displace iodine. lodine can’t displace chlorine or bromine This shows the reactivity trend - the halogens get less reactive as you go down the group. You can use this trend to predict how astatine might react. Since astatine is the least reactive halogen you’d predict it wouldn’t displace other halogens from their salt solutions

Question 13

What increases as you go down group 0?

Answer 13

Boiling point, melting point and density

Question 14

How can you use trends in physical properties of halogens to predict the properties of halogens further down the group?

Answer 14

You can use the trends in physical propeties from chlorine to iodine to predict the properties of halogens further down the group. For example, you can see that melting point increases down the group, and the colours of the halogens get darker so you could predict that astatine (which comes below iodine) would be a dark-coloured solid at room temperature and it is astatine is a black solid with a melting point of around 300 °C.

Question 15

What is the symbol equation of the reaction of sodium with water?

Answer 15

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

Question 16

What are the colours and physical states of chlorine, bromine and iodine?

Answer 16

Chlorine (Cl2) is a fairly reactive poisonous, green gas
Bromine (Br2) is a poisonous, red-brown liquid which gives off a orange vapour at room temperature
Iodine (I2) is a dark grey crystalline solid which gives off a purple vapour when heated

Question 17

How are metal halides formed?

Answer 17

Halogen + metal ——> salt (metal halide)

Question 18

Describe the reaction of sodium with water.

Answer 18

When sodium is added to water, the sodium melts to form a ball that moves around on the surface. It fizzes rapidly, and the hydrogen produced may burn with an orange flame before the sodium disappears.

Question 19

What is group 1?

Answer 19

Alkali Metals

Question 20

What is a displacement reaction?

Answer 20

This is when a more reactive element ‘pushes out’ a less reactive element. The elements in group 7 take part in displacement reactions.

For example, if chlorine water was added to potassium bromide, chlorine would displace bromide to form bromine and potassium chloride.

Question 21

What is group 7?

Answer 21

Halogens

Question 22

Give properties of metals. (5)

Answer 22

• Strong and hard
• High densities
• Malleable because layers of atoms in a pure metal can slide over each other.
• High melting points
• Good conductors of heat and electricity because the delocalised electrons in metals can carry an electrical current through the materials.

Question 23

What are the physical properties of alkali metals? (2)

Answer 23

• Low melting points and boiling points when compared with other metals
• Very soft - can be cut with a knife

Question 24

What is group 0?

Answer 24

Noble gases

Question 25

What is the symbol equation of the reaction of lithium with water?

Answer 25

2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)

Question 26

Describe the reactivity of group 7

Answer 26

A halogen atom only has to gain one electron to form a stable electronic structure. The easier it is for a halogen atom to attract an electron, the more reactive the halogen will be. As you go down group 6, it gets more reactive because it gets harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus.

Question 27

What would happen if you added iodine water (brown)to:

a) Potassium chloride
b) Potassium bromide
c) Potassium iodide

Answer 27

a) no reaction
b) no reaction
c) no reaction

Question 28

What is a metallic bond?

Answer 28

This is a bond between metals. Free electrons (negative) move around positive ions. Strong electrostatic force between positive metal ions + negative electrons.

Question 29

Describe the reaction of lithium with water.

Answer 29

When lithium is added to water, lithium floats. It fizzes steadily and becomes smaller, until it eventually disappears.