Short Notes:

Atoms are the basic building blocks of matter. Each atom comprises a nucleus which is made up of positively charged protons and electrically neutral neutrons. Negatively charged electrons orbit about this nucleus like planets around the sun. An atom size is determined by measuring its radius, taken from the centre of the nucleus to the orbit of the outermost electron. Their is a wide range of atomic sizes.

As atoms are so small, scientists record atom measurements in scientific notation.