Q. In the two elements and , the following relations are true.
and but , These elements are
( is atomic weight, is atomic number)

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Solution:

Given, and
Here, and
[ atomic weight, atomic number
But,
We know,
atomic weight number of protons number of neutrons and atomic number number of protons
So, number of neutrons atomic weight atomic weight
Any of two or more species of atoms or nuclei that have same number of neutrons are known as isotone. So, both elements are isotonic.