What is the atomic mass of an oxygen isotope that has 8 protons and 10 neutrons in its nucleus?

18.

Explanation:

Atomic Mass or Mass Number = number of protons + number of neutrons

= 8 + 10

= 18.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6