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.
Give the points of difference between sigma and pi molecular orbitals ?
| σ-Molecular orbital |  -Molecular orbital |
| 1. It is formed by the overlap of atomic orbitals along the internuclear axis. | 1. It is formed by the sidewise (lateral) overlapping of the atomic orbitals. |
| 2. Due to head on the overlap, the overlapping is maximum | 2. Due to sidewise overlap, overlapping is minimum. |
| 3. It consists of one electron cloud. | 3. It consists of two electron clouds, one lying above and the other lying below a plane passing through the nuclei. |
| 4. Its electron cloud is symmetrical about the internuclear axis. | 4. Its electron cloud is not symmetrical about the internuclear axis. |
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.
Draw the molecular orbital diagram for:
(i) Be2
(ii) B2 and predict bond order and magnetic properties.
Short Answer Type
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