Question

An isotone of ${}_{32}^{76}Ge$ is

• A. ${}_{32}^{77}Ge$
• B. ${}_{33}^{77}As$
• C. ${}_{34}^{77}Se$
• D. ${}_{34}^{78}Se$

Answer 1

Answer: (D)

Two nuclides are isotones if they have the very same neutron number but different proton number. For example, boron-$12$ and carbon-$13$ nuclei both contain $7$ neutrons, and so are isotones.
So, isotone of $Ge$ (atomic number $32$ , mass number $76$ ) is $Se$ (atomic number $34$ and mass number $78$).
The number of neutrons of $Ge$ here is $76-32=44$, now in $Se$ here, $78-34=44$ neutrons, due to a same number of neutrons, these are isotones.