JAMB - Chemistry (2024 - No. 122)
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
Penjelasan
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.
ā The element has atomic number of 15 (Phosphorus)