Chemistry

Problem

Which one of the following pairs of nuclides are isotopes of the same element? a)

{}_{7}^{14}\mathrm{N}

and

{}_{8}^{14}\mathrm{O}

{}_{6}^{14}\mathrm{C}

and

{}_{7}^{15}\mathrm{N}

{}_{8}^{16}\mathrm{O}

and

{}_{8}^{18}\mathrm{O}

{}_{11}^{23}\mathrm{Na}

and

{}_{12}^{23}\mathrm{Mg}