Atoms are too small. In fact, even the most powerful light-focusing microscopes can’t visualize single atoms. It is not possible actually to see the atoms but the nearest possibility to its direct evidence is by using an electron microscope.
“The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance. Atomic Masses depends upon the number of possible isotopes and their natural abundance.”
An ion is a charged atom. It is charged because the number of electrons does not equal the number of protons in the atom or molecule.