Ionic bonding:
An ionic bonding occurs when cations (positively charged) and anions (negatively charged) attract each other. In ionic bonding, atoms either loose electrons to become positively charged, in the case of metals, or gain electrons to become negatively charged, in the case of nonmetals. Molecules formed by ionic bonds are called salts.
Covalent bonding:
A covalent boding is the sharing of a pair of valence electrons between two atoms. When only one valence electron (electron in the valence shell (outermost shell)) is shared, the we call that a covalent bond. When two valence electrons are shared we call that a double covalent bond, such as the one found in an oxygen molecule.
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BioTeacher101