Chemistry - 2 The Periodic Table - 2.3 Group 1 - The Alkali Metals & 2.4 Group 7 - The Halogens

The alkali metals

- Lithium
- Sodium
- Potassium
- Rubidium
- Caesium
- Francium

The alkali metals - mnemonic

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Properties of alkali metals [6]:

- soft
- highly reactive (ch)
- low density
- (relatively) low melting and boiling point
- lustrous
- good thermal and electrical conductors

alkali metal + water →

metal hydroxide + hydrogen

alkali metal + oxygen →

metal oxide

alkali metal + chlorine/fluorine/bromine/iodine →

metal chloride/fluoride/bromide/iodide

Reactivity trend in group 1

reactivity increases as you descend the group

Melting and boiling point trend in group 1

melting and boiling point decreases as you descend the group

Why does reactivity increase as you descend group 1? [5]

- there is one electron in their outer shells
- as you descend, the atoms get larger
- the outermost electron is further away from the nucleus
- the electrostatic attraction between the nucleus and the electron is weaker
- the electron can be given up more easily (reaction)

How can we demonstrate the reactivity of group 1 metals?

place pieces of different alkali metals into a trough of water

The halogens

- Fluorine
- Chlorine
- Bromine
- Iodine
- Astatine

The halogens - mnemonic

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Properties of halogens [4]:

- forms coloured vapours (ch)
- toxic (ch)
- low melting points and boiling points
- poor thermal and electrical conductors

Halogens exist as ... molecules

diatomic

Diatomic molecule

consisting of two atoms combined by a covalent bond

Halogen + hydrogen →

hydrogen halide

Halide

a halogen bearing a negative charge

Hydrogen halides are ... at room temperature

gases

Hydrogen halides are ... when dissolved in water

acids

Reactivity trend in group 7

reactivity decreases as you descend the group

Melting and boiling point trend in group 7

melting and boiling point increase as you descend the group

Metal + halogen →

metal halide

some metal halides are ...

salts

What ions do halogens form?

1- ions

A more reactive halogen...

will displace a less reactive halogen from solutions of its salts