Atomic Structure MCQs for NEET — Chemistry Questions with Answers

The line spectrum of two elements is not identical because they have different energy level schemes. The electrons in different elements have different energy levels, and transitions between these levels result in the emission or absorption of specific wavelengths of light, giving rise to unique line spectra.

Bohr's atomic model can explain the spectrum of atoms or ions which are uni-electron species, such as hydrogen atoms, singly ionized helium (He⁺), or doubly ionized lithium (Li²⁺). The model is limited to systems with only one electron orbiting the nucleus.

The given atom has 2 K-shell electrons (1s), 8 L-shell electrons (2s and 2p), 11 M-shell electrons (3s, 3p, and 3d), and 2 N-shell electrons (4s). The total number of s-electrons, which have the spherical distribution, is 2 (1s) + 2 (2s) + 2 (3s) + 2 (4s) = 8.

$ E - = E_1 + E_2 now E = { hc \over \lambda} $ $ \therefore { 1 \over \lambda } = { 1 \over \lambda_1 } + { 1 \over \lambda_2 } $

$ \bar \nu = R Z ^2 [ { 1 \over n ^2 _1 } - { 1 \over n ^2 _f } ]cm ^ {-1} $ $ \bar \nu_H = R [ { 1 \over n ^2 _1 } - { 1 \over n ^2 _f } ]cm ^ {-1} $ $ \bar \nu_{He} = R Z ^2 [ { 1 \over n ^2 _1 } - { 1 \over n ^2 _f } ]cm ^ {-1} $

The work function of a metal is the minimum energy required to remove an electron from the metal surface. If the energy of the incident photon (E = hc/λ) is greater than the work function, the excess energy is given to the emitted electron as kinetic energy. Given: Work function = 4.2 eV, λ = 2000 Å = 2000 × 10^-10 m. Kinetic energy of the fastest photoelectron = hc/λ - Work function = (6.63 × 10^-34 × 3 × 10^8) / (2000 × 10^-10) - (4.2 × 1.6 × 10^-19) = 3.2 × 10^-19 J.

$ r_n = n^2 a_0 i.e. r \alpha n^2 r1 : r2 : r3 = 1^2 : 2^2 : 3^2 = 1 : 4 : 9 $

$ \lambda = { h \over mv } v = \lambda v \therefore \lambda = { v \over \nu } \therefore { v \over \nu } = { h \over mv } \therefore \nu = { mv^2 \over h } = { 2 K.E \over h } ( K.E = { 1 \over 2} mv ^2) $