Chemistry test 2

Halogens

• Reactivity of Group 7 non-metals decreases as you go down the group

• The melting / boiling point of the halogens increase

• The colour of the halogens gets darker

• Group 7 elements react in a similar way because they all have 7 electrons in their outer shell

• The reactivity of the halogens is determined by how easily it will gain one electron to achieve a full outer shell

• Reactivity decreases because:

  • Going down the group, the number of shells increases

  • The outer shell is therefore further away from the nucleus

  • There is less attraction between an incoming electron and the nucleus

  • It is harder to gain an electron

• Boiling and melting points increases due to:

• more energy being required to overcome the increased intermolecular forces

• This means that the melting / boiling point is higher

• The halogens are:

• Fluorine

• Chlorine

• Bromine

• Iodine

• Are diatomic

  • This means that they form molecules made of two atoms

  • The halogen atoms share electrons in a single covalent bond between them

  • These molecules are written as as F₂, Cl₂, etc.

  • The halogens form halide ions with a charge of -1

Alkali metals

React with non-metals to form ionic compounds

• E.g. sodium chloride is a white solid formed by the reaction between sodium and chlorine

• The metal ion will have a charge of +1

• The ionic compound formed is a white solid that dissolves in water to form a colourless solution

  React with water to produce a metal hydroxide and hydrogen gas

  • E.g. sodium reacts with water to form sodium hydroxide and hydrogen gas

• The reactivity of the Group 1 metals increases as you go down the group

• When a Group 1 element reacts, its atoms only need to lose the 1 electron in the outer shell

  • When this happens,+1 ions are formed

• Reactivity increases going down Group 1 because:

  • The number of shells increases

  • This means that the outermost electron gets further away from the nucleus

  • There are weaker forces of attraction between the outermost negative electron and the positive nucleus

  • Less energy is required to overcome the force of attraction

  • This means the outer electron is lost more easily

Transitional metals

The alkali metals share similar physical properties. For example, they:

• are soft (they can be cut with a knife)

• have relatively low melting points

• have low densities

The transition elements share some physical properties with all metals:

• they conduct electricity in the solid and liquid states

• they are shiny when freshly cut

Some properties of transition elements are different from those of the metals in group 1. Compared to other metals, most transition metals have:

• higher melting points

• higher densities

• greater strength

• greater hardness

Remember that these are typical properties – some transition metals may not show one or more of them. For example, mercury melts at just -39°C, so it is a liquid at room temperature.