It is used as a guideline to develop tests. It is open to revision and has not been disproved. An atom is the smallest particle that retains the properties of an element. Atoms have no net charge. The number of electrons is always equal to the number of protons.
Neutrons carry no net charge.
Atomic number refers to the number of proteins in an element's atom. Mass number refers to the combined number of protons and neutrons in the atomic nucleus of an element's atom. A chemical bond is a union between the electron structures of atoms. Atoms with vacancies in their outermost shell will give up, gain or share electrons with other atoms under suitable conditions. Atoms with vacancies tend to fill the vacancies by forming bonds with other atoms.