Question

a) Give the postulates of valence bond theory of coordination compounds.
b) Differentiate chemical reactions from nuclear reactions.

Answer 1

a)

1. The central metal atom/ion makes available a number of vacant orbitals equal to its coordination number.
2. These vacant orbitals form covalent bonds with the ligand orbitals.
3. A covalent bond is formed by the overlap of a vacant metal orbital and filled ligand orbitals. This complete overlap leads to the formation of a metal ligand, a bond.
4. A strong covalent is formed only when the orbitals overlap to the maximum extent. This maximum overlapping is possible only when the metal vacant orbitals undergo a process called 'Hybridisation'. The following table gives the coordination number, orbital hybridisation and spatial geometry of the more important geometrics.

Coordination number	Types of hybridisation	Geometry
2	$sp$	Linear
4	$s{p}^3$	Tetrahedral
4	$d^{2}s{p}^3$	Square planar
6	$d^{2}s{p}^3$	Octahedral
6	$s{p}^3{d}^2$	Octahedral

Magnetic moment
A species having atleast one unpaired electron, is said to be paramagnetic. It is attracted by an external field. The paramagnetic moment is given by the following spin- only formula
${\mu }_s=\sqrt{n(n+2)BM}$
${\mu }_s=$ Spin-only magnetic moment
$n=$ number of unpaired electrons
$BM=$ Bohr magneton, The unit which expresses the magnetic moment.
b)

	Chemical reaction	Nuclear reaction
	1.These reaction involve some loss, gain or overlap of outer orbital electrons of the reactant atoms.	Nuclear reaction involve emission of alpha, beta and gamma particles from the nucleus.
	2. A chemical reaction is balanced in terms of mass only.	Nuclear reaction is balanced in terms of both mass and energy.
	3. The energy-changes in any chemical reaction is very much less.	The energy changes is more in nuclear reactions.
	4. The energy is expressed in terms of kiloJoules per mole.	The energy involved is expressed in $MeV$ (million electron volts) per individual nucleus.
	5. No new element is produced since nucleus is unaffected.	New element/isotope may be produced during the nuclear reaction.