Atoms MCQs for NEET — Physics Questions with Answers

The NCERT text states: 'The wave character of the electron is ignored in Bohr’s theory. An orbit is a clearly defined path and this path can completely be defined only if both the exact position and the exact velocity of the electron at the same time are known. This is not possible according to the Heisenberg uncertainty principle.' Thus, ignoring wave character leads to a conflict with the uncertainty principle by assuming a well-defined orbit.

The NCERT text states: 'Bohr’s model include only one quantum number n. The new theory called quantum mechanics supportes Bohr’s postulate. However in quantum mechanics (more generally accepted), a given energy level may not correspond to just one quantum state. For example, a state is characterised by four quantum numbers (n, l, m, and s)...'

The NCERT text states: 'For complex atoms we have to use a new and radical theory based on Quantum Mechanics, which provides a more complete picture of the atomic structure.' Earlier, it is mentioned that quantum mechanics 'takes into account this dual behaviour of matter especially for sub-atomic particles and the uncertainty principle.'

The NCERT text states: 'Bohr model, though offering a satisfactory model for explaining the spectra of the hydrogen atom, could not explain the spectra of multi-electron atoms.' The inability to extend to multi-electron atoms suggests a failure to account for complex electron-electron interactions, which are absent in single-electron systems like hydrogen.

The text states: 'The French physicist Louis de Broglie explained this puzzle in 1923, ten years after Bohr proposed his model.' and 'We studied, in Chapter 11, about the de Broglie’s hypothesis that material particles, such as electrons, also have a wave nature.'

The context explicitly states: '(that is, $L_n = nh/2\pi$; n = 1, 2, 3 …).'

The context says: 'Louis de Broglie argued that the electron in its circular orbit, as proposed by Bohr, must be seen as a particle wave.'

The text states: 'De Broglie’s hypothesis...gave an explanation for Bohr’s quantised orbits by bringing in the wave-particle duality. The orbits correspond to circular standing waves in which the circumference of the orbit equals a whole number of wavelengths.' This is mathematically represented as $2\pi r_n = n\lambda$.

The context mentions: 'C. J. Davisson and L. H. Germer later experimentally verified the wave nature of electrons in 1927.'

The context explicitly states: 'From Chapter 11, we have $\lambda = h/p$, where $p$ is the magnitude of the electron’s momentum.' and also in the 'DUAL_NATURE_OF_RADIATION_AND_MATTER' chapter: 'The de Broglie wavelength ($\lambda$) associated with a moving particle is related to its momentum $p$ as: $\lambda = h/p$.'