Element: An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron.
Atomic number : The number of protons in the nucleus of an atom determines an element's atomic number.
Atomic number: It is the number of protons in one atom of a particular element. An undisturbed atom is electrically neutral, so the number of electrons in it is the same as its atomic number.
Atomic mass: The mass of an atom or a molecule is often called its atomic mass. Mass is a basic physical property of matter and strictly speaking there is no difference between mass and atomic mass.
Nomenclature : A system of names used in a particular discipline, as in medicine and surgery, anatomy and biochemistry, etc. A standard system of nomenclature presupposes the existence of an organized classification of the entities within that field.
Isotopes : Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes.
Allotropes : An allotrope is a variant of a substance consisting of only one type of atom. It is a new molecular configuration, with new physical properties. Substances that have allotropes include carbon, oxygen, sulfur, and phosphorous.