Groups 1 and 7

Question 1

Alkali metals with water equation

Answer 1

metal + water -> metal hydroxide + hydrogen

Question 2

Alkali metals with oxygen equation

Answer 2

metal + oxygen -> metal oxide

Question 3

Alkali metals trends

Answer 3

• react vigorously with water
• produces alkaline solution
• more reactive as you go down the group
• lose electrons more easily down the group
• low melting points (decreases down the group)
• soft (easily cut with knife)
• low densities (float on water)

Question 4

Halogens trends

Answer 4

• colour gets darker down the group
• boiling point increases down the group
• reactivity decreases down the group

Question 5

Alkali metals with halogens equation

Answer 5

metal + halogen -> metal halide

Question 6

Halogens with hydrogen equation

Answer 6

halogen + hydrogen -> hydrogen halide

Question 7

Displacement reactions

Answer 7

Where a more reactive element displaces (pushes out) a less reactive element from a compound. Can be used to test order of reactivity.

Question 8

Reduction

Answer 8

loss of oxygen and gain of electrons

Question 9

Oxidation

Answer 9

gain of oxygen and loss of electrons

Question 10

Redox reaction

Answer 10

Reactions where reduction and oxidation happen at the same time

Question 11

Observations for alkali metals

Answer 11

• fizzing (effervescence)
• metal floats and moves around on water
• metal melts
• sparks + flame produced (for potassium + below)
• hydrogen gas produced
• water with universal indicator turns purple

Question 12

Group 1 reactivity trend explanation

Answer 12

The atoms get larger, so the outer electron gets further from the nucleus.
The attraction between the nucleus and outer electron gets weaker – so the electron is more easily lost.

Question 13

Electron shielding

Answer 13

the blocking of valence shell electron attraction by the nucleus due to the presence of inner-shell electrons

Question 14

Chlorine

Answer 14

Cl2, green, gas at room temperature

Question 15

Bromine

Answer 15

Br2, red, liquid at room temperature

Question 16

Iodine

Answer 16

I2, grey, solid at room temperature

Question 17

Group 7 reactivity trend explanation

Answer 17

The halogens are non-metals and GAIN an electron. As you move down the group, the amount of electron shielding increases, meaning that the electron is less attracted to the nucleus. This makes it more difficult for the atom to gain the electron, resulting in a weaker reaction.