Answer:
The correct choice is E (47 neutrons, 35 protons, 36 electrons)
Explanation:
A ion of net charge -1 means that the ion wins an e-.
We dismiss options B and C.
We also dismiss option A because neutrons + protons = 81.
neutrons + protons = mass number
So we have E and C.
We see that C has 47 neutrons, 36 protons and 36 electrons and, as the atomic number matches the number of protons, we find out on the Periodic Table that the atomic number 36 represents to Krypton, a noble gas. It is impossible! A noble gas never can't be a ion of net charge.
Option E is correct, It is an isotope of Br.
Br has 35 protons (its atomic number)
47 neutrons, that's why it is an Isotope (Br has always 45 neutrons)
As usual, Br has 35 electrons, if it represents a ion of net charge -1, it menas it won 1 e-.
