Metals & Non-Metals (AQA GCSE Chemistry)

• The elements can be divided into two broad types: metals and non-metals
• Atoms of different elements which do not have a full outer shell of electrons, can try to achieve a full outer shell by gaining or losing electrons in chemical reactions
  • Elements that react by losing electrons to form positive ions are metals
  • Elements that do not form positive ions are non-metals; this includes elements that react by gaining electrons to form negative ions and Group 0 elements

• Most of the elements are metals and a small number of elements display properties of both types
  • These elements are called metalloids or semi-metals

• The metallic character of the elements decreases as you move across a period on the periodic table, from left to right, and it increases as you move down a group
• This trend occurs due to atoms more readily accepting electrons to fill their valence shells

• The metals that are further to the left on the periodic table do not have many electrons to remove from their outer shells
• As you descend the groups, the outer shell electrons become further away from the nucleus due to increasing atomic size
  • This weakens their attraction to the nucleus

• The further down the group an element is, the more easily it can react and lose its outer electron(s)
• For the non-metals which are placed on the right-hand side, the opposite is the case
• These elements have a lot of outer electrons, and it is more feasible for them to gain (or share electrons) to obtain a full outer shell
  • This is a key difference between metals and non-metals and influences their chemical behaviour

• It also clearly illustrates the important link between an element's atomic number and how it reacts as well as its position on the periodic table

• The general properties of most metals and non-metals are summarised below

A summary of the general properties of metals & non-metals