Question

Which of the following is true for the following isotopes of uranium
U${}^{235}$ and U${}^{238}$?

• A. both contain the same number of neutrons
• B. both contain the same number of protons, electrons and neutrons
• C. both contain the same number of protons and electrons but U${}^{238}$ contains three more neutrons than U${}^{235}$
• D. U${}^{238}$ contain three less neutrons than U${}^{235}$

Answer 1

The correct option is C both contain the same number of protons and electrons but U${}^{238}$ contains three more neutrons than U${}^{235}$

Natural Uranium contains $3$ radioactive isotopes $U^{234},U^{235}$ and $U^{238}$

$U^{238}$ has a mass number

(proton $92+$neutron $146$) $=238$

$U^{235}$ has mass number (proton $92+$ neutron$143$) $=235$

Hence we can say that both contain the same number of protons and electrons but $U^{238}$ contains three more neutrons than $U^{235}$