If a stable neutral atom has a mass number of 31, the number of electrons and neutrons respectively are
-
15 and 16
- 16 and 31
- 15 and 31
- 16 and 15
The correct answer is: A
Explanation
The only information we are given is the mass number, so we have to work our answer from the options.
Using the elimination method, options B and C are incorrect because when you add the numbers together, they give 47 and 46 respectively which is more than 31.
We are left with options A and D. However, the correct answer will be option A, since there are 15 electrons which invariably means, we also have 15 number of protons.
⇒ The element has atomic number of 15 (Phosphorus)
There is an explanation video available .