Atoms combine to form various types of substances. But what holds them together? Fundamentally, some forces of attraction hold atoms together in substances. These forces are called chemical bonds. Basically, the forces of attraction that lead to chemical bonding between atoms are electrical in nature. The electronic structure of an atom helps us to understand how atoms are held together to form substances. Atoms other than the noble gases have a tendency to react with other elements. These elements are reactive because they tend to gain stability by losing or gaining electrons. When atoms gain or lose electrons, they acquire the configuration of the next noble gas element. The tendency of metal atoms to lose electrons is called electropositivity. Whereas the tendency of non-metal atoms to gain electrons is called electronegativity. So, metals are electropositive and non-metals are electronegative elements.
Atoms can also acquire the configuration of the next noble gas element by sharing electrons.
Metals are electropositive in nature because all metal atoms lose electrons from their outermost shell in order to become stable and become positively charged. They have low ionization energy and low electronegativity allowing them to easily lose electrons. Therefore, they can form positive ions by losing electrons.
Example:
Na → Na+ + e-
Mg → Mg2+ + 2e-
Non-metals are electronegative in nature because all non-metals gain electrons in order to become stable and hence become negatively charged. They have high electronegativity and high electron affinity. So they can easily form negative ions by gaining electrons.
For example:
F + e- → F-