The bond formation is the important phenomenon, from which the present living world is derived.A bond is formed between two atoms to form a molecule, when they share electrons with each other.The prime classification of chemical bonds is of three types. They are ionic bond, covalent bond, and hydrogen bond. Ionic bond: Ionic bond is the result of electrons sharing between any two ions.Ions are formed when an atom loses or gains electron.If an atom loses an electron, then it forms monovalent cation(positive ion), since the positive charge of proton will be maximum in such case.Similarly An atom forms a anion or negative ion, when it gains an electron, where negative charge is maximum.This cations and anions (unlike charges) attracts and shares their electrons to form a neutral molecule. For instance,Sodium chloride (table salt) whose molecular formula is NaCl, is formed by combination of Na+ cation and Cl- anion.Sodium Na has a atomic no. of 11.It loses one electron to form Na+ with 10 electrons and 11 protons.(atomic no. denotes the no. of protons) Similarly, Chlorine atom with atomic no. 17, gains one electron to form Cl- anion with 18 electrons and 17 protons.Hence the NaCl is the result of gathering of these to monovalent ions (loses or gains only one electron). Covalent bond: From the word covalent, it is clear that two atoms going to share same no. of electrons with each other.It is like an give and take policy.Mostly covalent bonds are seen in molecules of carbon(organic molecules). For instance, Methane a fuel in our kitchens with molecular formula CH4(base to H) is the result of covalent bonding between one caebon atom and four hydrogen atoms.             Methane: Further there are two types of ionic bonds such as polar and non-polar.For instance water molecule is formed by polar covalent bond. Hydrogen bond: It is differ from the other two.This is not a major one to form a molecule, instead it is like a force between two molecules to form their respective structure. The universal water is present bcoz of this hydrogen bonding. This hydrogen bonding between water molecules is responsible for the high boiling point of water about 100 degree celsius and this is the reason why water does not evaporates rapidly............. See u with some more infos...............