I) Oxidation number

i) Oxidation number
The oxidation number (or oxidation state) is a number assigned to an element in a compound that represents the number of electrons lost or gained by an atom of that element when it forms a bond. It indicates the degree of oxidation (loss of electrons) or reduction (gain of electrons) of an atom.

ii) Ionic bond
An ionic bond is a type of chemical bond formed between two oppositely charged ions, typically a metal and a non-metal. It results from the complete transfer of one or more valence electrons from one atom to another, creating a cation (positive ion) and an anion (negative ion) that are attracted to each other.

iii) Covalent bond
A covalent bond is a chemical bond formed between two atoms by the sharing of one or more pairs of valence electrons. This type of bond typically occurs between two non-metal atoms, allowing both atoms to achieve a stable electron configuration.

iv) Metallic bond
A metallic bond is a type of chemical bond found in metals, characterized by a "sea" of delocalized valence electrons shared among a lattice of positively charged metal ions. These mobile electrons are not associated with any single atom, giving metals their characteristic properties like conductivity and malleability.

v) Hydrogen bond
A hydrogen bond is a weak intermolecular force of attraction between a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) and another nearby electronegative atom. It is a special type of dipole-dipole interaction.