If diamonds and pencils are made of carbon, how is it that pencils can write?

Context: While using a pencil, the core of the pencil slides
on the paper. In the process, the carbon atoms are forced to slide on the atoms
of the paper. While using a diamond on paper, the atoms of the material are so
tightly bound they have absolutely no interest in leaving. Each pencil has a
black-grey core surrounded by wood. When you sharpen the pencil, the core
becomes more exposed, and the pencil can write better. The "lead" of
a pencil is made from a mixture of graphite, a soft, opaque, gray to black
mineral, and clay. The clay strengthens and makes the graphite more durable.

Key points

·      
Role of
Carbon: Pencil cores are made of
carbon, too, but a different form called graphite. The carbons atoms in
graphite are arranged in sheets, like slices of bread in a sandwich. Each layer
contains carbon atoms connected to each other with three hands — that’s a very
strong bond. However, the bonds between sheets are weak. Each layer in this
arrangement is called graphene.

·      
Diamonds: When carbon atoms are arranged and stacked in
different ways, they have completely different properties. If the carbon atoms
arrange themselves in the form of an Egyptian pyramid-like structure, they form
a diamond. Diamonds are shiny, transparent, and the hardest material known in
nature.

·      
Discovery
of Graphene: Scientists conducted an
experiment, where they stuck cellophane tape on graphite and then ripped it
off. When they looked at the tape under a microscope, they found thin layers of
carbon stuck to it, i.e. graphene.