The size of the atom is of the order of:

The correct answer is Option (2) → \( 10^{-10}\,\mathrm{m} \)

The size of an atom (the radius of its electron cloud, for example the Bohr radius of hydrogen, \( 0.53\times10^{-10}\,\mathrm{m} \)) is about one angstrom, \( 1\,\mathrm{\mathring{A}} = 10^{-10}\,\mathrm{m} \).

The nucleus is far smaller, of the order of \( 10^{-15}\,\mathrm{m} \) to \( 10^{-14}\,\mathrm{m} \), which is why Option (4) cannot be the size of the atom itself.

NCERT (2026-27):
Alpha-Particle Scattering and Rutherford’s Nuclear Model of Atom – “… Rutherford’s experiments suggested the size of the nucleus to be about 10^–15 m to 10^–14 m. From kinetic theory, the size of an atom was known to be 10^–10 m, about 10,000 to 100,000 times larger than the size of the nucleus.”