- 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 react by gaining electrons to form negative ions are non-metals
- 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
An ion is an atom or molecule which has become charged through the loss or gain of one or more electron(s).
Metals will form positive ions when they react – when they lose electrons, the atom ends up with more positively charged protons than negatively charged electrons, which leaves it with an overall positive charge.
Non-metals will form negative ions when they react – when they gain electrons, the atom ends up with more negatively charged electrons than positively charged protons, which leaves it with an overall negative charge.
Positive ions are called cations and negative ions are called anions.
- 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
Atoms react to gain full outer shells by losing, gaining or sharing electrons.
The number of outer electrons an atom has determines its chemical properties and how it reacts.
- The general properties of most metals and non-metals are summarised below
A summary of the General Properties of Metals & Non-metals