Question

Which of the following is not an isotope of hydrogen atom?
(A) Protium
(B) Deuterium
(C) Tritium
(D) Platinum

Answer 1

Hint: Hydrogen has three isotopes. The three isotopes have different mass numbers. However, they have the same atomic number. In the elements mentioned in options, check which option has an atomic number different from that of hydrogen atom. The atomic number of hydrogen atoms is 1.

Complete step by step answer:
Hydrogen is the chemical element with the symbol "H" and the atomic number is 1. It has a standard atomic weight of 1.008 making it the lightest element in the periodic table.
It is the most abundant chemical in the universe, constituting roughly about 75% of the entire baryonic mass. Hydrogen exists in plasma states in non-remnant stars.
At standard temperature and pressure, hydrogen exists as a colourless, odourless, tasteless, non-toxic, and highly combustible gas. Hydrogen cannot exist in its elemental form in nature as it does not have a stable octet, it exists as a molecule made up of two hydrogen atoms.
Hydrogen readily forms covalent compounds with most non-metallic compounds. This is the reason why hydrogen exists mostly in the form of water or organic compounds on Earth.
Hydrogen has 3 main isotopes, protium deuterium and tritium having mass number 1, 2 and 3 respectively. In the given options, the one which is not an isotope of hydrogen is platinum.
So, the correct answer is “Option D”.

Note: The position of hydrogen in the periodic table is not clear. This is because hydrogen releases an electron and forms bonds with non-metals which is a characteristic feature of group 1 elements. On the other hand, hydrogen gains an electron and forms compounds with metals like sodium hydride, potassium hydride etc.