Question

atomic number
a. equals protons
b. identifies the element
c. equals electrons in an atom, but not in an ion
d. all of the above

Explanation:

The atomic number of an element equals the number of protons in its nucleus (a is correct). It also identifies the element (each element has a unique atomic number, so b is correct). In a neutral atom, atomic number equals the number of electrons (c: for neutral atoms, electrons = protons = atomic number; in ions, electrons differ, but the statement specifies "in an atom, but not in an ion"—so for neutral atoms, this holds). Thus, a, b, c are correct, so d (all of the above) is right.

Answer:

d. all of the above