Atoms, elements and compounds — AQA GCSE Chemistry
Test yourself on Atoms, elements and compounds with AQA GCSE practice questions.
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Atoms, elements and compounds explained
Each element has a unique chemical symbol, usually one or two letters.
Read the full explanation
The first letter is always a capital, and the second letter, if present, is lowercase. For example, O is oxygen, Na is sodium, and Fe is iron. These symbols are internationally recognised and are used in chemical equations and formulae. The symbol represents one atom of that element. When you write a formula such as H₂O, the symbols tell you which elements are present and the subscripts tell you how many atoms of each. Understanding symbols is essential for writing and interpreting chemical equations, and for calculating relative formula masses. The periodic table lists all elements with their symbols, and you are expected to know the symbols for the first 20 elements and some common transition metals.
Your focus
- Recall the chemical symbols for common elements.
- Interpret a chemical symbol as representing one atom of an element.
- Use chemical symbols to write formulae for simple compounds.
Atoms, elements and compounds exam tips
Marking Points
- State that each element has its own unique chemical symbol.
- Write the correct symbol for common elements, using capital and lowercase letters appropriately.
- Interpret a chemical symbol as representing one atom of that element.
- Use symbols to write chemical formulae for compounds.
- Recognise that symbols are used internationally and are listed in the periodic table.
Examiner Tips
- 💡Learn the symbols and names of the first 20 elements and common transition metals like iron, copper and zinc.
- 💡When writing formulae, ensure subscripts are used correctly to show the number of atoms.
- 💡In equations, use symbols rather than names to show you understand chemical notation.
Common Mistakes
- Writing symbols with incorrect capitalisation, such as 'na' instead of 'Na' or 'CO' for cobalt instead of 'Co'. Correction: use a capital first letter and lowercase second letter.
- Confusing the symbol with the name, for example thinking 'Na' stands for nitrogen. Correction: learn the symbols for common elements.
- Assuming a symbol represents a molecule rather than an atom. Correction: a symbol represents one atom of the element.