Edexcel IGCSE Chemistry · Spec 1.20-1.24
Groups, Metals & Non-metals
Groups and periods, and the properties of metals and non-metals.
Chemistry revision video
Groups, Metals & Non-metals
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Explained
Groups, metals and non metals
The periodic table is arranged so that position tells you about behaviour. Columns are groups and rows are periods. Elements in the same group have the same number of electrons in their outer shell, which is why they react in similar ways, and that single idea explains most of what follows.
Where the divide falls
Metals occupy the left and centre and make up the great majority of elements. Non metals sit to the right. The boundary runs as a rough diagonal step down the right hand side of the table.
Comparing the two
- Metals conduct electricity and heat. Most non metals do not, with graphite as the exception you are expected to know.
- Metals are usually strong and malleable. Non metals are typically brittle when solid.
- Metals generally have high melting points. Many non metals melt at low temperatures, and several are gases at room temperature.
- Metals form positive ions by losing electrons. Non metals form negative ions or bond covalently.
Group 1 metals are an exception to the strength point. They are soft enough to cut with a knife, which is why questions use them to check whether you have learned the pattern or the reasoning.
Why the noble gases do nothing
Group 0 elements have a full outer shell of electrons. There is no tendency to gain, lose or share, so they are extremely unreactive and exist as single atoms rather than in pairs.
Say full outer shell rather than saying the atoms are "happy" or "stable because they want to be". The full shell is the reason, and stating it plainly is what earns the mark.
What examiners say about this topic
Principal examiner reports for Edexcel International GCSE Chemistry record a precise loss of marks in Group 1 reactions. Some candidates referred to electrons being lost in the plural instead of a single electron, and that cost them the mark, because it implied more than one electron was lost, which is wrong for a Group 1 metal.
It is a small point with a clear lesson. A Group 1 atom loses one electron. A Group 2 atom loses two. Write the number, and write it in the singular when it is one.
The same reports note that candidates were generally successful at assigning state symbols in these equations, so those are marks worth securing.
Using group number
For the main groups, the group number tells you the number of outer shell electrons. Group 1 has one, Group 2 has two, Group 7 has seven and Group 0 has a full shell.
From that you can predict the ion. A Group 1 atom loses its single outer electron to form a 1 plus ion. A Group 7 atom gains one to complete its shell and forms a 1 minus ion. Questions asking you to predict a formula are usually testing exactly this chain of reasoning.
Spec 1.20-1.24
What you need to know
- Tell metals and non-metals apart
- Compare their properties
- Explain why the Group 0 noble gases are so unreactive
Active recall
Quick check
Answer each question before opening the answer.
Where are metals and non-metals found in the periodic table?
Metals are on the left and centre; non-metals are on the right (separated by a 'staircase').
What is a group and what is a period?
A group is a vertical column (elements with similar properties); a period is a horizontal row.
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