_______ are allotropes of carbon

Explanation

Allotropes are different forms of the same element in the same physical state, but with different properties due to variations in the arrangement of atoms. Carbon is an element with several allotropes, which include diamond, graphite, amorphous carbon, and fullerenes.

In this question, the correct answer isOption C: diamond and graphite. Both diamond and graphite are well-known allotropes of carbon, and they differ in their properties due to the arrangement of carbon atoms in their structures.

Diamond is a hard, crystalline form of carbon in which each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral arrangement. This structure results in very strong bonds, making diamond the hardest naturally occurring substance known. Diamond is also an excellent thermal conductor and has a high refractive index, which contributes to its sparkle as a gemstone.

Graphite, on the other hand, is a soft, slippery form of carbon in which each carbon atom is covalently bonded to three other carbon atoms, forming hexagonal layers. These layers are held together by weak van der Waals forces, which allow the layers to slide past each other easily. This property makes graphite an effective lubricant and a good conductor of electricity.

It is worth mentioning that amorphous charcoal and coke, mentioned in Option B, are also forms of carbon, but they are not considered true allotropes because they do not have well-defined crystal structures like diamond and graphite.