Question

What is the most common isotope of Chlorine?
A) \[^{35}C{l_{17}}\]
B) \[^{36}C{l_{17}}\]
C) \[^{37}C{l_{17}}\]
D) Both A and D

Answer 1

Hint: To identify the most common isotope we can detect it by knowing its stability and its abundance. Isotopes are the species having varying mass numbers, to be precise the same no. of protons but different no. of neutrons.

Formula used: \[^A{X_Z}\]
Where, \[A\] \[ = \]mass number and \[Z\] \[ = \]atomic number

Complete step by step answer:
Before getting this question solved, we need to know about the isotopes.
Isotopes are nothing but a small variant of any chemical element in which there is a difference in the number of neutrons but the number of protons will be the same in each atom.
Nomenclature of Isotope:
We can consider an example of Chlorine.
\[Cl\] has many isotopes out of which two are most common which are as follows:
\[^{35}C{l_{17}}\]and \[^{37}C{l_{17}}\]
In \[^{35}C{l_{17}}\]
 Where, \[35\]\[ = \] mass number
Mass number\[ = \]No. of protons + No. of neutrons
No. of protons \[ = \]$17$ (Atomic number of Chlorine)
No. of neutrons \[ = \]\[18\] (Mass number- No. of protons)
Atomic number\[ = \]\[17\]
In \[^{37}C{l_{17}}\]
Where, \[37\]\[ = \] mass number
Mass number\[ = \]No. of protons + No. of neutrons
No. of protons \[ = \]\[17\] (Atomic number of Chlorine)
No. of neutrons \[ = \]\[20\] (Mass number- No. of protons)
Atomic number\[ = \]\[17\]
Since, in the two cases mass number is changing and atomic number remains unchanged this can be termed as isotopes.

Option A) can be correct since \[^{35}C{l_{17}}\] is the most common isotope due to its stability which is \[76\% \] abundant and have stable half-life, but we have other options too thus we can look for other options.
Option B) This option is incorrect since, \[^{36}C{l_{17}}\] since it has a trace source and half-life is approximately about a year, thus it cannot be considered as the most common isotope.
Option C) can be correct since \[^{37}C{l_{17}}\] is the most common isotope due to its stability which is \[24\% \] abundant and have stable half-life, but we have other options too thus we can look for other options.
Option D) this is a correct option since it has both options which we consider to be right, thus both \[^{35}C{l_{17}}\] and \[^{37}C{l_{17}}\] are the most common isotopes of \[Cl\].

Hence, the correct answer is, ‘Option D’.

Note: Before solving the questions one must look at all the options given, and not to choose options in hurry. Read the question twice before answering and look at all the options carefully. \[^{35}C{l_{17}}\] and \[^{37}C{l_{17}}\] are the most common isotopes of Chlorine.