Question

Which of the following make up an isotonic triad?

• A. ${}_6^{14}C{,}_8^{16}O{,}_7^{15}N$
• B. ${}_{32}^{76}Ge{,}_{33}^{77}As{,}_{31}^{75}Ga$
• C. ${}_{18}^{40}Ar{,}_{19}^{40}K{,}_{20}^{40}Ca$
• D. ${}_{92}^{233}U{,}_{90}^{232}Th{,}_{94}^{239}Pu$

Answer 1

Answer: (A), (B)

The correct options are
A ${}_6^{14}C{,}_8^{16}O{,}_7^{15}N$
B ${}_{32}^{76}Ge{,}_{33}^{77}As{,}_{31}^{75}Ga$

Isotonic means having the same number of neutrons. And triad is any group of three. Together they comprise of isotonic triad which means any group of three atoms having same number of neutrons. So to find the number of neutrons in each atom we need to find the difference between atomic number and mass number. If it is same the triad is isotonic . If not the option is incorrect. So in option 1 all the atoms have neutrons 8. Hence option 1 is correct.

Similarly in option 2 all the atoms have neutrons 44 and hence option 2 is also correct.

Option 3 and 4 are incorrect