Band theory predicts that magnesium is an insulator. However, in practice it acts as a conductor due to

• A

  presence of filled 3s – orbital
• B

  overlap of filled 2p and filed 3s- orbital
• Correct answer
  C

  overlap of filled 3s and empty 3p-orbital
• D

  presence of unfilled 3p –orbital

Solution

The electronic configuration of Mg is
$1{\mathrm{s}}^2,\mathrm{}2{\mathrm{s}}^2,\mathrm{}2{\mathrm{p}}^6,\mathrm{}3{\mathrm{s}}^2,\mathrm{}3{\mathrm{p}}^0$
In it 3s – orbital is completely filed and 3p-orbital is empty. There is very small energy difference between 3s and 3p – orbitals. Thus, they overlap and make the Mg a conductor.

Band model of Mg

Hence, the correct answer is option: 'C'.