Question

Build an atom using 4 protons, 5 neutrons, and 4 electrons. What element is it?

Answer 1

Well, you got `"beryllium............"`, `""^9Be`.

Explanation:

There are 4 nuclear protons, i.e. `Z=4`, which specifies the element beryllium. How do you know? You look at the Periodic Table, and since you are doing your chemistry homework there will be one beside you now. The atomic mass is expressed by the number of massive particles, protons, and neutrons, and since we have 5 neutrons, the isotope is `""^9Be`.

Finally we can assign the charge. There are 4 protonic charges, and 4 electronic charges: the isotope is neutral.