what are the three constituent parts of an atom
Atoms and Elements. Ordinary matter is made up of protons, neutrons, and electrons and is composed of atoms. An atom consists of a tiny nucleus made up of protons and neutrons, on the order of 20,000 times smaller than the size of the atom. The outer part of the atom consists of a number of electrons equal to the number of protons, making the normal atom electrically neutral. A chemical element consists of those atoms with a specific number of protons in the nucleus; this number is called the atomic number. The atoms of an element may differ in the number of neutrons; atoms with different neutron numbers are said to be different isotopes of the element.