Question

1. observe: set the protons to 8 and the neutrons to 9. a. how is the isotope written at the top left of the gray box? b. what does the number next to the element name indicate?

Explanation:

A. The top - left number of an isotope notation is the mass number. Mass number (A)= number of protons + number of neutrons. Given 8 protons and 9 neutrons, A = 8+9=17. For 8 protons, the element is oxygen (O). So the isotope is written as $^{17}O$.
B. The number next to the element name in isotope notation is the mass number which represents the total number of protons and neutrons in the nucleus of the atom.

Answer:

A. $^{17}O$
B. The total number of protons and neutrons in the nucleus of the atom.