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  • The theory that can completely /properly explain the nature of bonding in Option: 1 Molecular orbital theory &nbs

The theory that can completely /properly explain the nature of bonding in[Ni(CO)_4]
Option: 1 Molecular orbital theory
 
Option: 2 Crystal field theory
 
Option: 3 Wemer's theory  
 
Option: 4 Valence bond theory
 
 

Answers (1)

best_answer

As we have learnt,

 

Molecular Orbital Theory -

Molecular orbital theory (MO theory) provides an explanation of chemical bonding that accounts for the paramagnetism of the oxygen molecule. It also explains the bonding in a number of other molecules, such as violations of the octet rule and more molecules with more complicated bonding that are difficult to describe with Lewis structures. Additionally, it provides a model for describing the energies of electrons in a molecule and the probable location of these electrons. Unlike valence bond theory, which uses hybrid orbitals that are assigned to one specific atom, MO theory uses the combination of atomic orbitals to yield molecular orbitals that are delocalized over the entire molecule rather than being localized on its constituent atoms. MO theory also helps us understand why some substances are electrical conductors, others are semiconductors, and still others are insulators. The table given below explains the major differences between the valence bond theory and molecular orbital theory.

 

Comparison of Bonding Theories

Valence Bond Theory

Molecular Orbital Theory

considers bonds as localized between one pair of atoms

considers electrons delocalized throughout the entire molecule

creates bonds from overlap of atomic orbitals (s, p, d…) and hybrid orbitals (sp, sp2, sp3…)

combines atomic orbitals to form molecular orbitals (σ, σ*, π, π*)

forms σ or π bonds

creates bonding and antibonding interactions based on which orbitals are filled

predicts molecular shape based on the number of regions of electron density

predicts the arrangement of electrons in molecules

needs multiple structures to describe resonance

  

 

Molecular orbital theory describes the distribution of electrons in molecules in much the same way that the distribution of electrons in atoms is described using atomic orbitals. Using quantum mechanics, the behavior of an electron in a molecule is still described by a wave function, Ψ, analogous to the behavior in an atom. Just like electrons around isolated atoms, electrons around atoms in molecules are limited to discrete (quantized) energies. The region of space in which a valence electron in a molecule is likely to be found is called a molecular orbital (Ψ2). Like an atomic orbital, a molecular orbital is full when it contains two electrons with opposite spin.

We will consider the molecular orbitals in molecules composed of two identical atoms (H2 or Cl2, for example). Such molecules are called homonuclear diatomic molecules. In these diatomic molecules, several types of molecular orbitals occur.

The mathematical process of combining atomic orbitals to generate molecular orbitals is called the linear combination of atomic orbitals (LCAO). The wave function describes the wavelike properties of an electron. Molecular orbitals are combinations of atomic orbital wave functions. Combining waves can lead to constructive interference, in which peaks line up with peaks, or destructive interference, in which peaks line up with troughs as shown in the figure below. In orbitals, the waves are three dimensional, and they combine with in-phase waves producing regions with a higher probability of electron density and out-of-phase waves producing nodes, or regions of no electron density.

A pair of diagrams are shown and labeled, “a” and “b.” Diagram a shows two identical waves with two crests and two troughs. They are drawn one above the other with a plus sign in between and an equal sign to the right. To the right of the equal sign is a much taller wave with a same number of troughs and crests. Diagram b shows two waves with two crests and two troughs, but they are mirror images of one another rotated over a horizontal axis. They are drawn one above the other with a plus sign in between and an equal sign to the right. To the right of the equal sign is a flat line.

(a) When in-phase waves combine, constructive interference produces a wave with greater amplitude. (b) When out-of-phase waves combine, destructive interference produces a wave with less (or no) amplitude.

 

-

 

 

The metal-carbonyl \pi is formed by the donation of a pair of electrons from a filled d orbital of metal into the vacant antibonding \pi* orbital of carbon monoxide.

Therefore, Option(1) is correct.

Posted by

Kuldeep Maurya

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