Question

In the two elements ${ }_{Z_{1}} A^{M_{1}}$ and ${ }_{Z_{2}} A^{M_{2}}$, the following relations are true.
$M _{1} \neq M _{2}$ and $Z _{1} \neq Z _{2}$ but $M _{1}- Z _{1}= M _{2}- Z _{2}$, These elements are
($M$ is atomic weight, $Z$ is atomic number)

• A. Isotonic
• B. Isobaric
• C. Isotopic
• D. Isoelectronic

Answer 1

Answer: (A)

Given, $z_{1} A^{M_{1}}$ and $z_{2} B^{M_{2}}$
Here, $M_{1} \neq M_{2}$ and $Z_{1} \neq Z_{2}$
[ $M=$ atomic weight, $Z=$ atomic number $]$
But, $M_{1}-Z_{1}=M_{2}-Z_{2}$
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.