The triad of nuclei that is isotonic is

The triad of nuclei that is isotonic is
  1. ${ }_{6}^{14} \mathrm{C},{ }_{7}^{15} \mathrm{~N},{ }_{9}^{17} \mathrm{~F}$
  2. ${ }_{6}^{12} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{19} \mathrm{~F}$
  3. ${ }_{6}^{14} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{17} \mathrm{~F}$
  4. ${ }_{6}^{14} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{19} \mathrm{~F}$

Solution

All contain $8$ neutrons (species containing the same number of neutrons are called isotonic).
Isotonic species are defined as the species which have the same number of neutrons.
No. of neutrons in:
${ }_{6} \mathrm{C}^{14}=14-6=8$
${ }_{7} \mathrm{~N}^{14}=14-7=7$
${ }_{9} \mathrm{~F}^{19}=19-9=10$
${ }_{7} \mathrm{~N}^{15}=15-7=8$
${ }_{9} \mathrm{~F}^{17}=15-7=8$
${ }_{6} \mathrm{C}^{12}=12-6=6$
${ }_{6} \mathrm{C}^{14},{ }_{7} \mathrm{N}^{15},{ }_{9} \mathrm{~F}^{17}$ are isotonic species. .

Asked in: JEE-TOPICTESTS-CHEMISTRY

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