The atomic radius of hydrogen atom is

[amp_mcq option1=”37 nanometer” option2=”37 picometer” option3=”17 picometer” option4=”57 picometer” correct=”option2″]

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UPSC CAPF – 2022

The atomic radius of a hydrogen atom is approximately 37 picometers (pm) when considered as a covalent radius, or about 52.9 pm for the Bohr radius. Given the options, 37 picometer is the closest and a commonly cited value for the covalent radius of hydrogen.

– The size of an atom is often described by its radius.
– Different definitions of atomic radius exist (e.g., covalent radius, van der Waals radius, Bohr radius) which yield different values.
– 1 picometer (pm) = 10⁻¹² meters.
– 1 nanometer (nm) = 10⁻⁹ meters = 1000 picometers.
– A radius of 37 nanometers would be extremely large, equivalent to 37,000 picometers, which is not the size of a hydrogen atom.

The Bohr radius (a₀) for the ground state of hydrogen is approximately 52.9 pm. The covalent radius of hydrogen, often determined from the H-H bond length in H₂ (about 74 pm), is taken as half of this length, i.e., 37 pm. The van der Waals radius of hydrogen is significantly larger, around 120 pm. The question does not specify which type of radius, but 37 pm is a valid and commonly used value for its covalent radius.

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