Читать книгу Foundations of Chemistry - Philippa B. Cranwell - Страница 111

Firstly, decide on the central atom. Carbon is the only element in the molecule that can have more than two bonds, so carbon must be the central atom. The carbon atom requires four more electrons to complete its octet.

To satisfy the octet rule, oxygen needs an extra two electrons and so shares two of its electrons with two from carbon, making a double bond. The two hydrogen atoms share one electron each with carbon to form two single bonds. Using a dot‐and‐cross diagram, it can be seen that there are three areas of electron density (remember, a double bond counts as one area). Therefore, to achieve minimum repulsion, the three areas spread out to be roughly 120° apart from each other, and the shape is trigonal planar or planar triangular.