Chemistry Notes on Chemical bonding

Valency:

Valency is the main point on which chemical bonding depends.
The valency of an element is the capacity to form chemical bonds and it is equal to the number of electrons in its atom.

Ions:

An ion is an electrically charged particle.
A positively charged particle is called a cation while a negatively charged particle is known as an anion.
A cation is formed due to the loss of an electron (Na⁺, H⁺).
An anion is formed due to the gain of an electron (F^-, Cl^-).

Types of chemical bonding:

Chemical bonding is of the following types depending upon the sharing of electrons or the transfer of electrons.

Electrovalent Bond:

The bond formed by the transfer of an electron from one atom to another is called an electrovalent bond or ionic bond.
The compound formed due to an electrovalent bond is called an electrovalent compound or ionic compound.
These bonds are formed between metals and non-metals.
Electrovalent compounds have high melting and boiling point.
They are conductors of electricity when dissolved in water.
They are soluble in water but not in organic solvents like alcohol.
e.g. Aluminium Oxide (Al₂O₃), Ammonium chloride (NH₄Cl), and Calcium chloride (CaCl₂)

Covalent Bond:

The bond is formed by the sharing of an electron between two atoms of the same or different elements, which is called a covalent bond and the compound formed due to this bonding is called a Covalent compound.
Covalent bonds may be single, double, or triple depending upon the number of sharing pairs of electrons.
Covalent compounds have low melting and boiling point.
They do not conduct electricity and are insoluble in water but dissolve in an organic compounds.
e.g. Alcohol (C₂H₅OH), Ammonia (NH₃), Ethane (C₂H₆), Methane (CH₄).

Coordinate and Dative Bond:

The bond is formed by the one-sided sharing of one pair of electrons between two atoms.
The main condition for the formation of a Coordinate bond is that the octet of one atom should be complete, having at least one lone pair of electrons and other atoms should have a deficiency of at least one pair of electrons.
The atom has a complete octet which provides the electron pair for sharing is known as donor.
The other atom which accepts the electron pair is called the acceptor.

Sigma Bond:

A bond is formed by the linear overlapping of atomic orbitals is called a sigma bond.
The extent of overlapping in a sigma bond is large so they are strong bonds.

Pi-bond:

This bond is formed by the lateral or sidewise overlapping of atomic orbitals.
Since the extent of overlapping is small so they are weak bonds.
e.g. in O_2, one bond is sigma and one is a pi bond.

Hydrogen bond:

When a hydrogen atom is present between the two most electronegative atoms then it is bonded to one by a covalent bond and to the other by a weak force of attraction which is called a hydrogen bond. e.g. Present in H₂O and HF.