Bohr's Atomic Model - MCQs

In Bohr's model, electrons move in:

• Straight lines

• Fixed circular orbits

• Elliptical paths

• Spiral patterns

Answer explanation

In Bohr's model, electrons are described as moving in fixed circular orbits around the nucleus, which is a key feature distinguishing it from other models of atomic structure.

According to Bohr, energy of an electron in a hydrogen atom is:

• Continuous

• Quantised

• Random

• Infinite

Answer explanation

According to Bohr's model, the energy levels of an electron in a hydrogen atom are quantised, meaning they can only take on specific discrete values, rather than being continuous or random.

What happens when an electron jumps from a higher to a lower energy level?

• Energy is absorbed

• The atom becomes unstable

• Energy is released in the form of light

• Nothing happens

Answer explanation

When an electron jumps from a higher to a lower energy level, it releases energy in the form of light. This process is known as photon emission, which is why the correct answer is that energy is released in the form of light.

The ground state of an atom refers to:

• When electrons are in the highest orbit

• When electrons are ionised

• The lowest energy level of an electron

• The mid-point energy level

Answer explanation

The ground state of an atom is defined as the lowest energy level of an electron, where electrons occupy the closest orbitals to the nucleus, minimizing their energy.

What is the process of an electron gaining energy and moving to a higher level called?

• Emission

• Ionisation

• Excitation

• Deactivation

Answer explanation

The process of an electron gaining energy and moving to a higher energy level is called excitation. During excitation, the electron absorbs energy, allowing it to transition to a more energetic state.

Which series in hydrogen spectrum appears in the visible region?

• Lyman

• Balmer

• Paschen

• Pfund

Answer explanation

The Balmer series is the only series in the hydrogen spectrum that appears in the visible region, with transitions occurring from higher energy levels to the second energy level, producing visible light.

Which of the following statements is TRUE?

• Line spectrum contains all wavelengths.

• Electrons continuously lose energy in orbits.

• Each line in the spectrum corresponds to a specific wavelength.

• Bohr's model applies to all elements.

Answer explanation

Each line in a line spectrum represents a specific wavelength emitted by electrons transitioning between energy levels, making this statement true. The other options are incorrect regarding the nature of spectra and Bohr's model.

The Brackett series occurs when electrons

• excited to n=2

• falls to n=2

• excited to n = 4

• falls to n = 4

Answer explanation

The Brackett series involves transitions where electrons fall to the n=4 energy level. Therefore, the correct choice is 'falls to n=4', as this describes the emission of light in this series.

Which series lies in the infrared region?

• Lyman

• Paschen

• Balmer

• None

Answer explanation

The Paschen series corresponds to transitions of electrons to the third energy level in hydrogen, emitting infrared radiation. In contrast, the Lyman and Balmer series emit ultraviolet and visible light, respectively.

Which of the following best describes a line spectrum?

• Contains all wavelengths

• Produced by solids only

• Consists of discrete lines

• Continuous and uninterrupted

Answer explanation

A line spectrum consists of discrete lines representing specific wavelengths emitted by atoms or molecules. This distinguishes it from a continuous spectrum, which contains all wavelengths without gaps.