Question

Find the correct number of protons and neutrons for the radioactive atom ${}^{99}Tc$?

• 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

Answer: (A)

43 protons and 56 neutrons

Mass number is 99. Atomic number is 43.

Number of protons $=$ atomic number $=$ 43.

Number of neutrons $=$ Mass number $-$ atomic number $=99-43=56$