In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure.
Diamond is an allotrope of carbon, in which atoms are arranged in a crystal structure called diamond cubic.
Diamond is the hardest and has the highest thermal conductivity of any natural material. These properties make it very useful for industrial purposes.
Graphite is also an allotrope of carbon in which atoms are arranged in the hexagonal arrangement. Graphite is the most stable form of carbon under the STP (standard temperature and pressure). It is used in pencils and electrodes.
Ethane is a hydrocarbon and second member of the alkane family after methane.
Methane is the first member of the alkane family having only one carbon atom.