Chemical symbols and formulae
Chemical symbols
Each A substance made of one type of atom only. is represented by its own chemical symbol. A chemical symbol:
- consists of one or two letters
- always starts with a capital letter, with any other letter in lower case
For example, the element mercury is shown as Hg. It must not be shown as HG, hg or hG.
The periodic table shows the names and symbols of the elements.
Learn more on atoms, elements and compounds in this podcast.
Listen to the full series on 大象传媒 Sounds.
Chemical formulae of elements
A A combination of symbols that indicates the chemical composition of a substance. is used to represent an element or A substance formed by the chemical union of two or more elements. in A chemical equation written using the symbols and formulae of the reactants and products, so that the number of units of each element present is the same on both sides of the arrow..
The formulae for most elements is just their symbol, but some Element that is a poor conductor of electricity and heat, and which forms acidic oxides. elements exist as A collection of two or more atoms held together by chemical bonds. that contain two The smallest part of an element that can exist. joined together. These molecules are called A molecule made up of only two atoms. The seven diatomic elements are iodine, bromine, chlorine, fluorine, oxygen, nitrogen and hydrogen. molecules. To show this, their formulae all have a A letter or number written below the line. number 2 in them. For example:
- iodine, I2
- bromine, Br2
- chlorine, Cl2
- fluorine, F2
- oxygen, O2
- nitrogen, N2
- hydrogen, H2
A mnemonic can be used to remember these elements:
IBring Clay For Our New House.