Question

Pls answer this question it's a bit urgent hope you answer the question. (pls answer in written form if possible. PLS) ​

Answer 1

Explanation:

look no. of electron is equal to no. of proton...

and atomic no. of an element gives no. of electron...

since mass no. is 40 and atomic no. is 20...

so no. of neutrons is 40-20 = 20