Question

For the radioactive atom ${}^{99}Tc$, what is the correct number of protons and neutrons?

• A. 43 protons and 56 neutrons
• B. 43 protons and 99 neutrons
• C. 56 protons and 43 neutrons
• D. 56 protons and 99 neutrons
• E. Cannot be determined

Answer 1

The correct option is A 43 protons and 56 neutrons

Technetium has an atomic number of $43$. Thus, it has $43$ protons.

Its mass number is $99$. Mass number constitutes the total number of protons and neutrons.

The number of protons is $43$.

Mass number is $99$.

Thus, number of neutrons $=99$ $-$ $43=56$)

Thus, $43$ protons, $56$ neutrons.

Option $A$ is correct.