Isotopes of Hydrogen MCQ - Practice Questions & Answers

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Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason

Assertion A: Hydrogen is an environment friendly fuel.

Reason R: Atomic number of hydrogen is 1 and it is a very light element.

In the light of the above statements, choose the correct answer from the options given below

A is true but is false

is false but is true

Both and are true and is the correct explanation of

Both and are true but is NOT the correct explanation of A

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Occurrence of Hydrogen - Isotopes of Hydrogen

Hydrogen is the most abundant element in the universe with helium being second. Oxygen is the most abundant element on the earth by mass.

About Hydrogen :

Hydrogen is the first element in the periodic table. However, its placement in the periodic table has been a subject of discussion in the past.
Hydrogen is the lightest atom with only one electron.
Hydrogen has the simplest atomic structure among all the elements around us in Nature.
In atomic form it consists of only one proton and one electron. However, in elemental form it exists as a diatomic (H₂) molecule and is called dihydrogen.
It forms more compounds than any other element.

Isotopes of Hydrogen : Hydrogen has 3 isotopes. And these isotopes differ from each other because of presence of different number of neutrons.

Protium, $^{1}_{1}H$
Deuterium, $^{2}_{1}H$ or D
Tritium, $^{3}_{1}H$ or T

Since the isotopes have the same electronic configuration, they have almost the same chemical properties. The only difference is in their rates of reactions, mainly due to their different enthalpy of bond dissociation However, in physical properties these isotopes differ considerably due to their large mass differences. It is to be mentioned that Tritium is the only radioactive isotope of Hydrogen and it emits $\beta$ - particles.

Position and Resemblance of Hydrogen in Periodic Table

Hydrogen was obtained by Henry cavendish in 1766 by the action of acids on metals.

Debatable position of Hydrogen in periodic table:

Hydrogen has electronic configuration 1s¹. On one hand, its electronic configuration is similar to the outer electronic configuration (ns¹ ) of alkali metals , which belong to the first group of the periodic table. On the other hand, like halogens (with ns 2np⁵ configuration belonging to the seventeenth group of the periodic table), it is short by one electron to the corresponding noble gas configuration, helium (1s² ). Hydrogen, therefore, has resemblance to alkali metals, which lose one electron to form unipositive ions, as well as with halogens, which gain one electron to form uni negative ion. Like alkali metals, hydrogen forms oxides, halides and sulphides. However, unlike alkali metals, it has a very high ionization enthalpy and does not possess metallic characteristics under normal conditions. In fact, in terms of ionization enthalpy, hydrogen resembles more with halogens, $\Delta_iH$ of Li is $520\ kJ\ mol^{-1}$ , F is $1680\ kJ\ mol^{-1}$ and that of H is $1312\ kJ\ mol^{-1}$ . Like halogens, it forms a diatomic molecule, combines with elements to form hydrides and a large number of covalent compounds. However, in terms of reactivity, it is very low as compared to halogens. Hence due to it's unique behaviour, it is placed separately in the periodic table.