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Small molecules - AQAInterpreting dot and cross diagrams

A covalent bond is a shared pair of electrons. Covalent bonding forms molecules. Substances with small molecules have low melting and boiling points, and do not conduct electricity.

Part of Chemistry (Single Science)Bonding, structure and the properties of matter

Interpreting dot and cross diagrams

Dot and cross diagrams show how are shared in . The table shows dot and cross diagrams for an element, chlorine, and two compounds.

Three substances with their formula, structure and a dot and cross diagram.

Question

Deduce the formula of water using information from the table above.

Double and triple bonds

Some contain a , 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鈮, showing that it has three shared pairs of electrons.

Oxygen and nitrogen with their formulas, structures and dot and cross diagrams.

Question

Give the structure of an oxygen molecule, using one line to represent each shared pair of electrons.