Long Answer TypeWhich of the following combinations of orbtials are allowed in LCAO method (considering z-axis to be molecular axis) and sketch the shapes of molecular orbitals formed by their addition and subtraction:
(i) s and pz
(ii) px and px
(iii) pz and py
(iv) s and px.
Short Answer TypeGive the number of electrons which occupy the bonding molecular orbital in H2+ H2 and He2.
What do you understand by bond order? How is it related with bond length and bond energy? Explain on the basis of bond order that He2 molecule does not exist.
Long Answer TypeUsing LCAO method for the formation of molecular orbitals in case of homonuclear diatomic hydrogen molecule.
According to LCAO method, molecular orbitals are formed by the combination of atomic orbitals.
In the case of H2 molecule, each H-atom consists of one atomic orbital (i.e. 1s) having one electron each.
On combining these two atomic orbitals of two H-atoms, we get two molecular orbitals for H2 molecule. One molecular orbital is lower in energy called bonding molecular orbital and its wave function is obtained by linear addition of wave functions of two
H-atoms Ψ (1s) + Ψ Ψ (1s) → Ψ MO. (bonding MO called a is ).
The other molecular orbital with higher energy is called antibonding molecular orbital and its wave function is obtained by linear subtraction of wave functions of two H-atoms as:
Ψ (1s) – Ψ (1s) → Ψ MO
(Antibonding M.O. called).
The energy level diagram of H2 molecule can be given as:
Draw the molecular orbital diagram for:
(i) Be2
(ii) B2 and predict bond order and magnetic properties.
Short Answer Type
Switch
