JEE Advance - Chemistry (1988 - No. 1)
The triad of nuclei that is isotonic is
$${}_6^{14}C$$, $${}_7^{15}N$$, $${}_9^{17}C$$
$${}_6^{12}C$$, $${}_7^{14}N$$, $${}_9^{19}C$$
$${}_6^{14}C$$, $${}_7^{14}N$$, $${}_9^{17}C$$
$${}_6^{14}C$$, $${}_7^{14}N$$, $${}_9^{19}C$$