Which of the following covelent network solids is referred to as pencil lead?

Options

A. Corundum
B. Carborundum
C. Quartz
D. Graphite

Answer

4

Explanation

Graphite consists of two dimensional sheets of six-membered rings ,the atoms in each sheet are offset slightly from the atoms in the neighboning sheets.
The layers (sheets) are held together by the weak van der Waals forces.The strong covalent bonds in graphite account for its hardness.However graphite is slippery to the touch and is effective as a lubricant because the layers can slide over one another.
Graphite is used in pencils and ribbons made for computer printers and type writers.