Definition - What does Atom mean?
The atom is one of the basic building blocks that make up everything that we see in our physical world. Every form of matter is made from matter. Every molecule is made from atoms. There are 90 types of naturally forming atoms and scientists have been able to synthetically construct 25 more. Atoms consist of subatomic particles called protons, neutrons and electrons.
Safeopedia explains Atom
Atoms are the smallest component of any element in the periodic table. Atoms consist of a nucleus that contains a combination of protons and neutrons, and one or more electron, which is bound to the nucleus by electrical attraction. The number of protons determines the type of element the atom is and the number of neutrons determine which isotope of an element it is.