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 O2, 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.
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