Answer:
C. atomic symbol and number of protons.
Explanation:
number of protons in the nucleus, but differ in the number of neutrons. The nucleon number is equal to the total number of protons and neutrons in the nucleus. ... The atomic mass number A is equal to the total number of protons and neutrons.
Two isotopes of the same element must have the same atomic symbol and number of protons.
ISOTOPES:
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