Chemical Bonding

Chemical bonding is the force that holds atoms together in a molecule or compound. Atoms form bonds because doing so lowers their total energy and gives them a more stable electron arrangement — usually a filled outer shell. Without chemical bonding, no molecules, no materials, and no living organisms would exist.

The three main types are ionic bonds (electron transfer between metal and non-metal), covalent bonds (electron sharing between non-metals), and metallic bonds (delocalised electron sea in metals). Coordinate bonds and hydrogen bonds are additional important types tested in JEE and NEET.

A sigma (σ) bond is formed by head-on overlap of orbitals along the internuclear axis. It is the first bond in any covalent bond and is stronger and more stable. A pi (π) bond forms by lateral (side-to-side) overlap of p-orbitals above and below the axis. Double bonds contain one σ + one π; triple bonds contain one σ + two π.

CO₂ is linear (sp hybridised carbon), so its two C=O bond dipoles point in exactly opposite directions and cancel each other out. Net dipole moment = zero, making the molecule non-polar overall. H₂O, by contrast, is bent (due to lone pairs), so its bond dipoles do not cancel — it has a net dipole moment and is polar.

Bond order = (Number of electrons in bonding MOs − Number of electrons in antibonding MOs) ÷ 2. A bond order of 1 = single bond, 2 = double bond, 3 = triple bond. Zero means the molecule is unstable and does not exist. Fractional bond orders are possible (e.g., O₂⁻ has bond order 1.5).