Chemistry I / Hybridisation and Molecular Orbitals
Practice question · True or false

The helium molecule He2\mathrm{He_2} is unstable because its bond order is zero.

Hints
  1. Fill the MO diagram for four electrons and count.
  2. Two bonding and two antibonding electrons cancel exactly.
Show the answer

True

Why

True, four electrons fill both the bonding and the antibonding orbital, giving (22)/2=0(2-2)/2 = 0. With no net bonding there is nothing to hold the atoms together, which is why helium is monatomic.

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