24. A radioisotope of argon, 35 Ar, lies below the "band of stability: (n/p ratio too...

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Answer::::::Positron emission

³⁶Ar₁₈ = Stable isotope

³⁵Ar₁₈ unstable isotope=radioisotope

n/p(17/18) for ³⁵Ar₁₈ is 0.94<1.

This indicated that it contains more protons than the neutrons(Mass number-Atomic number). It can undergo positron emission to increase number of neutrons by 1. So, The positron emission or beta decay will convert Ar-35 to Cl-35, stable isotope.

³⁵Ar₁₈ + _-1e⁰---> ³⁵Cl₁₇ + ₀v⁰

proton inside a nucleus is converted into a neutron and releases a positron and an electron neutrino. n/p ratio of produced 35-Cl is nearly 1.

Here is the information about other options as well,

Beta emission- Atomic number will increase by 1.

So number of neutrons will decrease and n/p will go even lower.

Neutron emission- Mass number Decreases by 1. Number of neutrons will decrease and n/p will be lower.

Alpha emission- Decreases atomic number by 2 and mass number by 4. So, Neutrons will be deccrease by 4. n/p will be lowered.

Fission- Decay of an atom into lighter nucleus.