Hello Guys, No need to worry about Bond angle comparison problems, Watch full lecture and be expert in Bond Angle. Let’s start:-
Polyatomic molecule has more than one bonds which are formed by overlap of atomic or hybrid
orbitals and due to directional nature of the hybrid or atomic orbitals these bonds make angles between
them. The angles between the lines representing the two bonds are known as bond angles and are
measured by X-ray diffraction and spectroscopic methods. Because of the constant atomic vibrations,
the bond angles thus measured are really average bond angles. The shapes of the molecules are dependent
on the bond angles. The molecule of methane, therefore, is tetrahedral because of the H—C—H bond
angles of 109.5°, the molecule of water is V shaped because of the H—O—H bond angles of 104.5°
and the molecule of NH3 is pyramidal because of H—N—H bond angle of 107°
Bond angles mainly depend on the following three factors:
Hybridization: Bond angle depends on the state of hybridization of the central atom
Hybridization: sp3, Bond angle: 109, Example: CH4
Hybridization: sp2, Bond angle: 120, Example: BCl3
Hybridization: sp, Bond angle: 180, Example: BeCl2
Generally s- character increase in the hybrid bond, the bond angle increases.
Lone pair repulsion: Bond angle is affected by the presence of the lone pair of electrons at the central atom. A lone pair of electrons at the central atom always tries to repel the shared pair (bonded pair) of electrons. Due to this, the bonds are displaced slightly inside resulting in a decrease of bond angle.
Electronegativity: If the electronegativity of the central atom decreases, bond angle decreases.
One should also keep in mind:-
Triple bonds repel other bonding-electrons more strongly than double bonds.
Double bonds repel other bonding-electrons more strongly than single bonds.
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