Answer:
30, 50
Explanation:
Hello,
In this since an element's atomic number is equal to the number of protons in its atom, we can infer that selenium's atomic number is 30. Moreover, due to the fact the the neutrons are equal to the atomic mass minus the atomic number or the number of protons, by knowing the number of neutrons we compute the atomic as follows:

Thus, answer is 30, 50.
Best regards.
Neon belongs to 2nd Period & 18th Group
A. Its temperature will rise continuously until it completely melts
I don't believe that any of the other answers are correct because the ice cannot stay at a certain temperature if it is melting.
Isotope - the same element, but different atomic mass so 1)35 Cl and 37 Cl