Question

level 2
what does the number \15.999\ represent in this symbol?
a. number of electrons
b. number of neutrons
c. atomic number
d. atomic mass
oxygen 8 o 15.999

Explanation:

In the periodic - table, for an element, the number below the element symbol is the atomic mass. For oxygen with symbol O, 15.999 is its atomic mass which is the weighted average mass of its isotopes.

Answer:

D. Atomic mass