Chemistry MCQs for NEET — Practice Questions with Answers

The expression $mvr = \frac{nh}{2\pi}$ imposes the condition of quantization of energy of an electron in an atom, where m is the mass of the electron, v is its velocity, r is the radius of the orbit, n is an integer (principal quantum number), and h is Planck's constant. This condition arises from the quantization of angular momentum.

According to Bohr's model, an electron can revolve around the nucleus in a stable orbit without emitting energy if the orbit houses a whole number of de Broglie waves. This condition is known as the quantization of angular momentum.

According to Sommerfeld's modification of Bohr's atomic model, only circular orbits are possible for electrons in the K shell. For higher shells (L, M, N, etc.), elliptical orbits are also allowed.

The wavelength of a spectral line is inversely proportional to the energy difference between the initial and final energy levels involved in the electron transition. It is independent of the nuclear charge, electron velocity, and the number of electrons undergoing the transition.

The Stark effect is the splitting or shifting of spectral lines of atoms or molecules due to the presence of an external electric field. It is named after Johannes Stark, who discovered this phenomenon in 1913.