Define chemical bonding and electro theory of valency

 Chemical Bonding and Electro-Theory of Valency:

• Chemical bonding is the process by which atoms are held together in molecules or ions.
• The electro-theory of valency states that the chemical behavior of an element is determined by the number of electrons in its outermost energy level, or valence shell.
• The number of electrons in the valence shell is referred to as the element's valency.
• Elements with a valency of one or two tend to form ions by losing or gaining electrons, respectively, while elements with a valency of four or more tend to form covalent bonds by sharing electrons.