In a nucleus of atomic number Z = 19, atomic mass number 39, the number of electrons, protons, neutrons, and total nucleons, respectively, will be
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 0, 19, 20 and 39
The question asks about the nucleus, not the atom. A nucleus contains only protons and neutrons; the electrons are outside it.
\( \text{electrons in the nucleus} = 0 \)
\( \text{protons} = Z = 19 \)
\( \text{neutrons} = A - Z = 39 - 19 = 20 \)
\( \text{nucleons} = A = 39 \)