Chemical formulae of elements

A chemical formula is used to represent an element or compound in balanced chemical equations.

The formula for most elements is just its chemical symbol. For example:

  • helium, He
  • lithium, Li
  • beryllium, Be
  • boron, B
  • carbon, C
  • neon, Ne
  • sodium, Na
  • magnesium, Mg

Some non-metal elements exist as molecules that are made up of two atoms joined together. The formulae of these elements are the element's symbol followed by a subscripted '2'. 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:

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It's important to remember which elements exist as molecules, and which do not. Take care to use the correct form in chemical equations involving these elements.

What are the chemical formulae of the elements neon, nitrogen and sodium?

  • Ne
  • N2
  • Na