Question

What is different for isotopes of uranium?
A.) Number of protons
B.) Number of planetary electrons
C.) Atomic masses
D.) Atomic number

Answer 1

The isotopes are the substance which have the same atomic number but different mass number. The atomic number does not constitute protons but the mass number depends on the number of protons.

Complete step by step answer:
As the uranium element has the atomic number as $92$. Uranium is a naturally occurring radioactive element. All the isotopes of uranium are radioactive in nature. The isotopes are two or more forms of the same element. These elements have the same atomic number but different mass number. As we know that the atomic number is the number of protons that are present in every atom of an element. As isotopes have the same atomic number so we can say that the isotopes have the same number of protons in them. Also, we know that the mass number of an element is the total number of protons and neutrons that is present in the atom of an element. As the mass number of isotopes is different from each other, mass numbers include protons and neutrons as we have the same number of neutrons in isotopes so with the mass number of the isotopes the number of neutrons will differ from each other.
In this question, for uranium there are many known isotopes of it such as uranium $(234)$, uranium $(235)$, uranium $(238)$, uranium $(232)$, uranium $(233)$ etc. As we know that each isotope of uranium has an atomic number $92$ and different mass number. Therefore, isotopes of uranium different in the number of neutrons and not in the number of protons.

Hence, option C.) is the correct answer.

Note: Always remember that all the isotopes of uranium are unstable and radioactive. But isotopes like uranium $(238)$ and uranium $(235)$ have half lives which are sufficiently long to have allowed them to still be present in the solar system.