The stability of the following carbocations follows the order:
$I. (CH_3)_3C^{\oplus}$
$II. (CH_3)_2C^{\oplus}(OCH_3)$
$III. CH_3CH_2CH_2CH_2^{\oplus}$
$IV. CH_3CH^{\oplus}CH_2CH_3$

Due to the presence of an unpaired electron,free radicals become .......

State True or False for the following statements:
$(i)$ $\mathop{C}\limits^{+}H_3$ and $CH_3\mathop{C}\limits^{+}H_2$ both are primary carbocations.
$(ii)$ $(CH_3)_3\mathop{C}\limits^{+}$ is a tertiary carbocation and all carbons are $sp^3$ hybridized.
$(iii)$ $\mathop{C}\limits^{+}H_3$ is trigonal planar.
$(iv)$ $CH_4$ is not trigonal planar.

Stability order of the following carbocations:
$(i) CH_3 - C^{+}(OCH_3) - CH_3$
$(ii) CH_3 - C^{+}(CH_3) - CH_3$
$(iii) CH_3 - NH - C^{+}H_2$
$(iv) CH_3 - C^{+}H_2$

Arrange the following carbocations in decreasing order of stability.

Which free radical structure will show the maximum resonance? (Given: $\phi = C_6H_5$)