Atomic Number and Isotopes - MCQs with answers

ANSWER: c. Isotope

Explanation: Isotopes are defined as the elements having same atomic number but they differ in their mass number and chemical characteristics.

Eg: Carbon - diamond and graphite. Uranium - ₉₂U²³⁴, ₉₂U²³⁵, ₉₂U²³⁸

ANSWER: b. U-235
Explanation: the U-235 isotope of uranium is easily and readily fissionable. When a neutron enters a U-235 atom there is a possibility that the nucleus will split and release the enormous amount of energy that binds the nucleus together. The uranium nucleus ejects two or three neutrons resulting in chain reaction.

ANSWER: 931.4 MeV

Explanation: from Einstein’s law, W = mc₂

1 amu = 1.66 * 10^-27 *(3*10⁸)²

= 1.494 * 10^-10 J

1 eV = 1.602 * 10^-19 J

Also, 1 J = 1/ (1.602 * 10^-13) MeV

1 J = 1/ (1.494 * 10^-10) amu

1 amu = (1.494 * 10^-10) / (1.602 * 10^-13)

= 931 MeV