Which among the following statements with respect to carbon is/are correct? 1. Carbon forms the basis for all living organisms and many things we use 2. Carbon shows tetra-valency and the property of catenation 3. Carbon forms covalent bonds with itself and other elements 4. Carbon forms compounds containing triple and tetra bonds between carbon atoms Select the correct answer using the code given below :

The correct answer is C, 1, 2 and 3. Statements 1, 2 and 3 are true, but carbon never forms a quadruple, or tetra, bond between two carbon atoms.

Carbon has four electrons in its outer shell, so it shares electrons to form four covalent bonds; this is its tetravalency. It can also join with other carbon atoms in long chains, branches and rings, a property called catenation. These two features give millions of carbon compounds, from fuels and plastics to proteins, fats and DNA, which is why carbon is the basis of life. Between two carbon atoms the bond can be single, as in ethane, double, as in ethene, or triple, as in ethyne, but never quadruple.

A is wrong because statements 2 and 3 are also correct. B is wrong because statement 3 is also correct; carbon's bonds are covalent. D is wrong because statement 4 is false and statements 1 and 3 are left out.

Exam tip: carbon shows tetravalency and catenation; carbon-carbon bonds go only up to triple, as in ethyne.