The ionic radii of ${\mathrm{C}}^{4-}$ and ${\mathrm{O}}^{2-}$ are $2.60 \mathrm{\AA }$ and $1.40 \mathrm{\AA }$, respectively, the ionic radius of ${\mathrm{N}}^{3-}$ ion will be:

$\mathrm{M} \left(\mathrm{g}\right)\to {\mathrm{M}}^{+} \left(\mathrm{g}\right)+{\mathrm{e}}^{-}; \mathrm{\Delta H}=100 \mathrm{eV}$

$\mathrm{M} \left(\mathrm{g}\right)\to {\mathrm{M}}^{2+} \left(\mathrm{g}\right)+2{\mathrm{e}}^{-}; \mathrm{\Delta H}=350 \mathrm{eV}$

Which of the following is the correct statement with respect to the above reactions?

The atomic number of elements $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ are $\mathrm{Z}–1, \mathrm{Z}, \mathrm{Z}+1$ and $\mathrm{Z}+2,$ respectively. If $\mathrm{B}$ is a noble gas, choose the correct options from the following statements.

a. $\mathrm{A}$ is an element with very high electron affinity.

b. $\mathrm{C}$ is an element that forms a tripositive ion.

c. ${\mathrm{A}}^{-1}, \mathrm{B}, {\mathrm{C}}^{+1}$ and ${\mathrm{D}}^{+2}$ are isoelectronic species.

Choose the correct statements for element ${}_9{}^{19}\mathrm{M}.$

a. Formation of ${\mathrm{M}}^{-}$ is an endothermic process.

b. It's anion is isoelectronic with neon.

c. It has the smallest size in its period.

d. It has the highest electron gain enthalpy in its group.