a group is a vertical column of elements

consists of 18 groups of elements

a period is a horizontal row of elements

consists of 7 periods of elements, numbered 1 to 7

decrease in metallic properties and an increase in non-metallic properties across a period

this is because across the period, the atom becomes less likely to lose electrons

soft and can be cut easily

low melting and boiling points

low densities

alkali metal

reactivity increases down the group

stored in oil to prevent them from reacting with air and water

High melting and boiling point

Most transition metals (except mercury) have very high melting and boiling points because of strong metallic bonding.

High densities

Halogens have low melting and boiling points.

Halogens are coloured

Diatomic molecules

Colour becomes darker down the group

Size of atom increases down the group

Reactivity decreases down the group

A more reactive halogen displaces a less reactive halogen from its halide solution

monoatomic non-metals

colourless gases in room temp

low melting & boiling temp

insoluble in water

unreactive (have full valence shell)

increase in metallic properties and a decrease in non-metallic properties

this is due to the size of the atom increases going down a group, so the outermost electrons of the element will be further away from the attractive force of the nucleus