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Chemical bonding is a force in Nature that binds various chemical constituents like atoms, ions, etc., together. Chemical bonds are formed to get stability with a release of energy.
Hybridisation is a process of mixing atomic orbitals to form new hybrid orbitals having different energies and shapes than the atomic orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory.
Bond Angle
A bond angle is a geometric angle between two adjacent bonds. A bond angle is defined as the angle between the lines representing the orbitals that contain the bonding electrons. It helps determine the shape and can be expressed in degrees.
Hybridisation
Hybridisation is the process of intermixing orbitals having slightly different energies in order to redistribute their energies, resulting in the formation of a new set of orbitals of equivalent energies and shapes.
Features of Hybridisation
(i) Orbitals having almost equal energy take part in hybridisation.
(ii) The number of atomic orbitals mixed equals the number of hybrid orbitals produced.
(iii) Hybridisation can indicate the geometry of a covalent molecule.
(iv) Hybrid orbitals can form more effective bonds than pure atomic orbitals.
Conditions necessary for hybridisation:
(i) Orbitals of valence shells take part in hybridisation.
(ii) Orbitals involved in hybridisation must have almost equal energy.
(iii) In hybridisation, the promotion of electrons is not a necessary condition.
(iv) In some cases, filled orbitals of valence shells also take part in hybridisation.
Valence Shell Electron Pair Repulsion (VSEPR) Theory
This theory says that:
1. The number of electron pairs found in the valence shell of the central atom determines the geometry of various molecules and ions.
2. Electron pairs try to stay as far away as possible to obtain a minimum repulsive state.
3. When similar atoms of only the bonded electron pairs surround the central atom, the repulsive interactions are identical, and the molecular geometry is regular.
4. When only the bonded electron pairs of dissimilar atoms surround the central atom, the repulsive interactions are not equivalent. Hence, the molecule’s geometry will not be regular.
5. When both bonded pairs (bp) and lone pairs (lp) of electrons surround the central atom, repulsive interactions are not equivalent. Hence, the geometry of the molecule will be irregular.
The repulsive interactions decrease in the order:
lone pair-bond pair < bond pair-bond pair < lone pair – lone pair
The Hybridisation of Chlorine Trifluoride
To learn about the molecular geometry and bond angle of chlorine trifluoride, we need to discuss its hybridisation. When we talk about the hybridisation of chlorine trifluoride, we have to consider its central atom, chlorine. The central atom contains 7 valence electrons, while ClF3 consists of 3 bond pairs and 2 lone pairs. The valence-shell electronic configuration of Cl is given as 3s2, 3px2, 3py2, 3pz1, 3d.
When chlorine combines with fluorine atoms to form ClF3, three unpaired electrons are required to create a bond with three F-atoms. One paired electron of Cl in the 3p subshell remains as a lone pair or unpaired.
As a result, during hybridisation, one 3s, three 3p, and one of the 3d orbitals participate in this process, which leads to the formation of five sp3d hybrid orbitals. Now, two hybrid orbitals will contain a pair of electrons, and three hybrids will have unpaired electrons, which will overlap with the 2p orbital of F to form single bonds.
The central atom of chlorine requires three unpaired electrons to bond with three F-atoms.
ClF3 now consists of 3 bond pairs and 2 lone pairs.
When one 3s, three 3p, and one of the 3d orbitals of chlorine participate in hybridisation, then five sp3d hybrid orbitals are formed.
Molecular Geometry
Molecular geometry, also known as the molecular structure, is the three-dimensional structure or arrangement of atoms in a molecule. Let’s discuss the molecular geometry and bond angle of chlorine trifluoride.
ClF3 Molecular Geometry and Bond Angles
The structure of chlorine trifluoride consists of one chlorine atom surrounded by three fluorine atoms. In its structure, there are two lone pairs of electrons attached to the central chlorine atom. The chlorine atom forms three covalent bonds with its surrounding fluorine atoms in a stable state. The hybridisation of the central chlorine atom is sp3d.
The molecular geometry of ClF3 is said to be T-shaped. ClF3 acquires such a shape because two lone pairs take up equatorial positions as they require more space and greater repulsions. They are arranged in a trigonal bipyramidal shape with 3 bonds and 2 lone pairs. There is also an asymmetric charge distribution found around the central atom.
The molecular geometry and bond angle of chlorine trifluoride is trigonal bipyramidal with a 175° F-Cl-F bond angle.
Conclusion
Chemical bonds are formed when electrons of different atoms interact to create a more stable arrangement than when these atoms are apart.
The molecular geometry and bond angle of ClF3 is T-shaped, with one short bond of 1.598 Å and two long bonds of 1.698 Å along with a F-Cl-F bond angle of 175°. This structure validates the prediction of VSEPR theory, which says lone pairs of electrons occupy two equatorial positions of a hypothetical trigonal bipyramid.
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