According to current theory, a major reason for bonding is

According to current theory, a major reason for bonding is to gain the stability of the octet formation. In order for an octet (8 parts) formation to be stable, there has to be a bond achieved among the elements which comprise it. 
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Covalent bond   a chemical bond formed by two electrons that are shared between two atoms
ionic bond    a chemical bond formed by the electrostatic attraction between ions
metallic bond    a bond characteristic of metals in which mobile valence electrons are shared among positive nuclei in the metallic crystal

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom