Question

explain the difference in properties of diamond and graphite.

-why is graphite black while diamond is not?

-why is graphite very conductive while diamond is not a good conductor of electricity?

-why is graphite soft while diamond is hard

Answer 1

Graphite is black because it absorbs white light and refelects no light. Whenever any substance absorbs light from visible region, our eyes see the color complementary to it. But if a substance absorbs all the colors from white light and reflects no color, then the color of substance appears to be black. However, diamond is colorless because it doesn't absorb white light. White light pases through it making it transparent or colorless. Some diamonds are colored like yellow. It is because of the presence of impurities in it like nitrogen.

Graphite is a good conductor of electricity because of the presence of free electron. In graphite each carbon is bonded to three carbon atoms. Since carbon has 4 electrons in valence shell so one of the electrons in carbon is free i. e. It is not bonded to any other carbon atom. Despite a non metal, it conducts electricity and this free electron is responsible for its conductivity. On the other hand diamond is a poor conductor of electricity because it doesn't possess any free electron. In diamond, each carbon is bonded to four other carbon atoms so there is no free electron to conduct electricity.

Graphite is soft while diamond is hard. It happens because of the difference in structure and bonding between carbon atoms. In graphite each carbon is in a sp² hybridized state. Each carbon is bonded to three carbon atoms through sigma bonds resulting in the formation of hexagonal layers. The forces of attraction between atoms in different layers is weak vander Walls forces. The layers can detach from each other because of which it has soft and slippery nature. However, in diamond strong covalent bonds are present because each carbon is in sp³ hybridized state and is  bonded to four carbon atoms through four covalent bonds forming a tetrahedral structure. Thus, diamond exists as a three dimensional network solid. Thus, strong forces between catbon atoms is responsible for hardness of diamond.