Apply the rules / principles to fill the E.C. of homonuclear diatomic molecular ion. It includes Aufbau’s Principle, Pauli’s exclusion Principle & Hund’s rule of maximum multiplicity.
What is electronic configuration of H2+ molecular ion
H2+ has only 1 electron. It occupies the lowest energy level.
E.C. for H2+ ion = sigma 1s1
Bond order = 1/2 ( Nb – Na )
Na = 0e- Nb = 1e- [ Nb = bonding electron ] [ Na = antibonding electrons ]
- Bond order of H2+ ion = 1/2 [ 1 – 0 ] = 1/2
- Stability of H2+ ion = Bond order is positive. Therefore, it is stable but less.
- Magnetic behaviour = Paramagnetic [ 1 unpaired electron ]
What is electronic configuration of H2 molecule
H2 has only 2 electrons. It occupies the following energy levels:
E.C. for H2 = sigma 1s2, sigma* 1s0
Bond order = 1/2 ( Nb – Na )
Na = 0e- Nb = 2e- [ Nb = bonding electron ] [ Na = antibonding electrons ]
- Bond order of H2+ = 1/2 [ 2 – 0 ] = 1
- Stability of H2 = Bond order is positive. Therefore, it is stable.
- Magnetic behaviour = Diamagnetic [ all electrons are paired ]
What is electronic configuration of H2- molecular ion
H2- has only 3 electrons. It occupies the following energy levels:
E.C. for H2 = sigma 1s2, sigma* 1s1
Bond order = 1/2 ( Nb – Na )
Na = 1e- Nb = 2e- [ Nb = bonding electron ] [ Na = antibonding electron ]
- Bond order of H2- = 1/2 [ 2 – 1 ] = 1/2
- Stability of H2- = Bond order is positive. Therefore, it is stable but less.
- Magnetic behaviour = Paramagnetic [ 1 electron is unpaired ]
What is electronic configuration of He2 molecular ion
He2 has only 4 electrons. It occupies the following energy levels:
E.C. for He2 = sigma 1s2, sigma* 1s2
Bond order = 1/2 ( Nb – Na )
Na = 2e- Nb = 2e- [ Nb = bonding electron ] [ Na = antibonding electron ]
- Bond order of H2- = 1/2 [ 2 – 2 ] = 0
- Stability of He2- = Bond order is zero. Therefore, He2 is not stable & hence will not exist.
Check out the post on Molecular orbital configuration of O2 & N2 here :
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