Physics · Chemistry

Atomic Structure and Spectra

149 Questions

Atomic structure and spectra questions cover the Bohr model, quantum numbers, and electron transition calculations. These topics are fundamental to the physics and chemistry syllabi of competitive exams. Solving these builds confidence in handling atomic physics problems.

Bohr atomic modelHydrogen spectrum seriesElectron binding energyQuantum numbersDe Broglie wavelength

Atomic Structure and Spectra Questions

Multiple choice

What affects the ionisation energy of an element?

Ionisation energy of an atom or molecule describes the minimum amount of energy required to remove an electron from the atom or molecule in the gaseous state.

X   +  energy---->  X+ + e-

  1. Atomic size

  2. Electron affinity

  3. Electronegativity

  4. Neutron

  5. Proton
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In small atoms, electrons remains close to the  nucleus and they have more nuclear attraction, so more energy is required to remove electrons from small atoms. In small atoms, electrons remains close to the nucleus and they have more nuclear attraction, so more energy is required to remove electrons from small atoms.

Multiple choice

The hydrogen emission spectrum consists of several series of lines, named after their discoverers. Which of the following spectral series of lines is/are found in the infrared region?

  1. Lyman, Balmer and Paschen series

  2. Balmer, Paschen and Pfund series

  3. Paschen, Brackett and Pfund series

  4. Paschen, Balmer and Pfund series

  5. Lyman, Balmer and Pfund series
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Paschen, Brackett, and Pfund series of lines are found in the infrared region.

Multiple choice

Which of the following statements is not true?

  1. Hydrogen has the simplest line spectrum among all the elements.

  2. Absorption spectrum is formed when atoms or molecules are excited from a lower energy level to a higher energy level.

  3. Emission spectrum is formed when atoms or molecules are de-excited from a higher energy level to a lower energy level.

  4. Line Spectra are also known as molecular spectra.

  5. Band spectra is formed due to the vibrations and rotations of atoms in molecules.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct because this statement is not true. Line spectra are also called atomic spectra because the lines represent wavelengths radiated from atoms when electrons change from one energy level to another.
Band spectra are also known as molecular spectra because they are produced when the emitting substance is in the molecular state.

Multiple choice

The treatment of hydrogen atoms prescribed by Bohr can be generalised to

  1. describe the energy level structure and electromagnetic radiation spectra of hydrogen-like ions
  2. predict fine structure of atomic spectral lines
  3. provide a method to calculate relative intensities of spectral lines

  1. Only 1

  2. Only 2

  3. Only 3

  4. Both 1 and 2

  5. 1, 2 and 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The treatment of hydrogen atoms prescribed by Bohr can be generalised to describe the energy level structure and electromagnetic radiation spectra of hydrogen-like ions, i.e.  a positive nucleus orbited by a single electron.

Multiple choice

Which of the following statements is/are incorrect? A. Balmer series falls in the ultraviolet range of electromagnetic radiation. B. The emission and absorption spectra of hydrogen like atoms is explained nicely by Bohr’s concept of stationary state of electrons. C. Atomic spectrum is band spectrum while molecular spectrum is a line spectrum.

  1. Only A

  2. Only B

  3. Only C

  4. Only A and B

  5. Only A and C
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Wrong statement: Balmer series falls in the ultraviolet range of electromagnetic radiation.

Balmer series falls in the visible range of electromagnetic radiation.

Wrong statement: Atomic spectrum is a band spectrum while molecular spectrum is a line spectrum.

Atomic spectrum is line spectrum while molecular spectrum is a band spectrum.

Multiple choice

Bohr model can explain

  1. the spectrum of hydrogen atom only

  2. the spectrum of an atom or ion containing one electron only

  3. the spectrum of hydrogen molecule

  4. the solar spectrum

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bohr model can explain the spectrum of an atom or ion containing one electron only.

Multiple choice

Which of the following statements is correct?

  1. The different energy levels are equally spaced.

  2. The energy of the electron decreases as the value of n increases.

  3. The energy of the electrons in an atom is negative.

  4. Bohr's theory explains the spectrum of multi-electron atoms.

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An electron in an atom has negative energy because it is in a bound state. That means that it cannot escape the atom unless it is given energy.

Multiple choice

Which one of the following is paramagnetic in nature?

  1. Iron

  2. Hydrogen

  3. Oxygen

  4. Nitrogen
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Paramagnetic substances are attracted by magnetic fields due to the presence of unpaired electrons. Oxygen has two unpaired electrons in its molecular orbital structure, making it paramagnetic.

Multiple choice

In which case, the wavelength emitted is minimum?

  1. An electron jumps from 2nd to 1st level

  2. An electron jumps from 3rd to 2nd level

  3. An electron jumps from 4th to 3rd level

  4. An electron jumps from 5th to 4th level
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  Applying the Rydberg's equation 1/λ = R0[1/n12 - 1/n22] . We get 1/λ = R0 [3/4] or λ = 1.33/R0. This value of wavelength is the least among the given options.

Multiple choice

Radius of hydrogen atom is of the order of _____ .

  1. 1 nm

  2. 1 A�

  3. 1 cm

  4. 0.1 A�
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The atomic radius of a hydrogen atom is approximately 0.05 nm, which is equivalent to 0.5 Angstroms (A). Among the choices, 1 Angstrom is the closest order of magnitude.