MCQ Detailed View

Hydrogen is the simplest and lightest element in the periodic table. It usually consists of one proton in its nucleus and one electron outside it. Deuterium is an isotope of hydrogen. Isotopes are atoms of the same element that have the same number of protons (and thus the same atomic number) but a different number of neutrons, which changes their atomic mass.

In ordinary hydrogen (also called protium), the nucleus contains only one proton and no neutron, giving it an atomic mass of approximately 1 atomic mass unit (amu). In deuterium, the nucleus contains one proton and one neutron, giving it an atomic mass of about 2 amu. Both have the same atomic number (1), meaning they are the same element chemically, but they differ in weight because deuterium has an extra neutron.

This difference in mass causes some physical and nuclear properties of deuterium to vary slightly from normal hydrogen. For example, deuterium is used in heavy water (D₂O), which is applied in nuclear reactors as a neutron moderator. It also plays an important role in studies of chemical reaction mechanisms and fusion research.

Deuterium does not have a different atomic number from hydrogen because both have exactly one proton, which defines the element. The only difference lies in the atomic weight, making option 3 (Same atomic number and different atomic weight) the correct answer.

This concept belongs to Chemistry, specifically atomic structure and isotopes, which are fundamental in understanding elements, their reactions, and their behavior in different physical and nuclear processes.