The ElementsOxford AQA IGCSE Chemistry: Revision notes
Section 1
What are elements made of?
All substances are made of tiny particles called atoms. An element is a substance made of only one sort of atom — every atom in a pure element is the same type.
Elements are the simplest chemical substances: they cannot be broken down into anything simpler by chemical means.
Section 2
How many elements are there?
There are about 100 different elements, and each one is unique. All of these elements are displayed and organised in the periodic table, which arranges them so that elements with similar properties are grouped together.
Every known substance in the universe is either an element itself, or a compound/mixture built from combinations of elements.
Section 3
Chemical symbols
Each element is represented by a unique chemical symbol, a shorthand of one or two letters used internationally.
- The first letter is always a capital; the second letter (if present) is always lower case
- Some symbols come directly from the English name, e.g. O for oxygen, C for carbon
- Some symbols come from other languages (mainly Latin), e.g. Na for sodium (from natrium), Fe for iron (from ferrum)
Writing element symbols with the wrong capitalisation (e.g. 'CO' instead of 'Co' for cobalt) changes the meaning entirely — CO is carbon monoxide, a compound.
Section 4
Elements vs compounds vs mixtures
It is important to distinguish elements from other types of substance:
| Substance type | Description |
|---|---|
| Element | Made of only one type of atom |
| Compound | Made of two or more different elements chemically combined |
| Mixture | Two or more substances (elements and/or compounds) not chemically combined |
Only elements contain a single type of atom throughout.
Must Know
- All substances are made of atoms
- An element is a substance made of only one type of atom
- There are about 100 different elements
- Elements are displayed and organised in the periodic table
- Each element has a unique chemical symbol (e.g. O for oxygen), always starting with a capital letter
- Elements differ from compounds (two+ elements chemically combined) and mixtures (not chemically combined)
That's the notes covered.
Carry on to the next subtopic.