“Atom is the smallest particle of an element, which can take part in a chemical reaction.”
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.
“An ion formed by removing (positive ion), or adding (negative ion), one or more electrons from a molecule M to form M• or M•• ”