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.
Define bond order. What informations are conveyed by bond order?
Bond order may be defined as half the difference between number of electrons in bonding molecular orbitals and the number of electrons in antibonding molecular orbitals, i.e.,
Information conveyed by Bond Order:
(i) If the value of the bond order is positive, it indicates a stable molecule and if the value of the bond order is negative or zero, it means that the molecule is unstable and is not formed.
(ii) The dissociation energy of the molecule is directly proportional to the bond order of the molecule i.e. greater the bond order, greater is the bond dissociation energy.
(iii) Bond length of the molecule is inversely proportional to the bond order of the molecule i.e. greater the bond order, the shorter will be the bond length.
(iv) Knowing the bond order, the number of covalent bonds between the atoms in the molecule can be predicted. Bond order of a molecule is equal to the number of covalent bonds between the atoms in the molecule.
(v) If the bond order is fractional, the molecule will definitely be paramagnetic. However, if the bond order is the whole number, the molecule may or may not be paramagnetic.
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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