Deduce the formula of water using information from the table above.
The dot and cross diagram shows that a water molecule is made up of one oxygen atom joined to two hydrogen atoms, so the formula of water is H2O.
Some molecules contain a double bond, which consists of two shared pairs of electrons. For example, oxygen molecules consist of two oxygen atoms joined together. Oxygen atoms can form two covalent bonds, so to link the two oxygen atoms together, a double bond forms between them.
A nitrogen molecule is made up of two nitrogen atoms joined together. Nitrogen atoms can form three covalent bonds, so a triple bond forms between them. The structure of nitrogen is N≡N, showing that it has three shared pairs of electrons.
Give the structure of an oxygen molecule, using one line to represent each shared pair of electrons.