How atoms form the chemical compounds or molecules

In this paper atomic structure and valence of element were studied. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. How atoms form the compounds are explained by valence number. The valence of an atom is a measure of its combining capacity with other atoms when it forms chemical compounds or molecules. This paper shows the law of atomic density change with quant energy and the law of dependence valence number from density of atom, first time in the literature. Valence number was defined by number of proton and number of electron.