Question

The oxide of nitrogen which forms dimer is __________.

• A. nitrogen oxide
• B. nitrous oxide
• C. nitrogen dioxide
• D. none of the above

Answer 1

The correct option is C nitrogen dioxide

${NO}_2$ exists as dimer $N_2{O}_4$.
The lewis structure of nitrogen dioxide requires that the central atom nitrogen be bonded to one oxygen through a double covalent bond and to another oxygen through a three electron bond. So one electron remains unpaired. If two nitrogen dioxide units dimerize through N-N bonds formation the odd electron on N couples with that of another molecule. So it is dimagnetic in nature.