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 nuclear reactions nuclear structure nuclei atomic nuclei physics

If the energy of an electron in Hydrogen atom is given by expression, $-1312 /{ n }^{ 2 }kJ{ mol }^{ -1 }$, then the energy required to excite the electron from ground state to second orbit is 

  1. $328 kJ{ mol }^{ -1 }$
  2. $656 kJ{ mol }^{ -1 }$
  3. $984 kJ{ mol }^{ -1 }$
  4. $1312 kJ{ mol }^{ -1 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\begin{array}{l} E=-1312\left( { \frac { 1 }{ 4 } -1 } \right)  \ =\frac { { -1312\times 3 } }{ 4 }  \ =328\times 3 \ =984\, kJmo{ l^{ -1 } } \ Hence, \ option\, \, C\, \, is\, \, correct\, answer. \end{array}$

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

The helium atom is two times heavier than a hydrogen molecule. At $298$ K, the average kinetic energy of a helium atom is:

  1. Two times that of hydrogen molecule

  2. Same as that of a hydrogen molecules

  3. Four times that of a hydrogen molecules

  4. Half that of a hydrogen molecule
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the formula of average kinetic energy:


$K.E. = \dfrac 32 KT$

K.E does not depend upon mass.


$\therefore$ At the same temperature, K.E will be same.

Hence, option $B$ is correct.

Multiple choice collisions in one dimension collisions work, energy and power mechanics physics

A free hydrogen atom in ground state is at rest. A neutron of kinetic energy $K$ collides with the hydrogen atom. After collision hydrogen atom emits two photons in succession one of which has energy $2.55\ eV.$
(Assume that the hydrogen atom and neutron has same mass)

  1. Minimum value of $K$ is $25.5\ eV.$
  2. Minimum value of $K$ is $12.75\ eV.$
  3. The other photon has energy $10.2\ eV$ if $K$ is minimum.
  4. The upper energy level is of excitation energy $12.75\ eV$.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

To excite the atom to the n=3 level (energy -1.51 eV from -13.6 eV), the energy required is 12.09 eV. If it emits a 2.55 eV photon (n=3 to n=2), the remaining energy must be 10.2 eV (n=2 to n=1). The minimum energy K must account for the excitation and the recoil energy of the atom.

Multiple choice

the basic unit of a chemical element

  1. atom

  2. molecule

  3. substance

  4. heat
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An atom is the smallest unit of an element that retains the chemical properties of that element.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Hydrogen atom does not emit X-rays because

  1. it contains only a single electron

  2. energy levels in it are far apart

  3. its size is very small

  4. energy levels in it are very close to each other
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hydrogen is the least energetic element. Even the most energetic line that hydrogen emits (when an electron drops down from the second shell to the first) has only enough energy to be an ultraviolet photon. This is because the energy levels in hydrogen atom are very close. So hydrogen atoms do not emit X rays.

Multiple choice

Which quantum phenomenon is responsible for the cooling of quantum systems to ultra-low temperatures?

  1. Laser cooling

  2. Sympathetic cooling

  3. Doppler cooling

  4. Adiabatic cooling
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Laser cooling is a technique that uses the absorption and re-emission of photons to cool atoms and molecules to ultra-low temperatures. It works by selectively exciting and de-exciting atoms or molecules with laser light.

Multiple choice

Which quantum property is responsible for the quantization of energy levels in atoms and molecules?

  1. Wave-particle duality

  2. Quantum superposition

  3. Quantum entanglement

  4. Quantum tunneling
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Wave-particle duality is the fundamental property of matter that it can exhibit both wave-like and particle-like behavior. In the context of quantum thermodynamics, wave-particle duality leads to the quantization of energy levels in atoms and molecules.

Multiple choice

Which quantum phenomenon is responsible for the quantization of angular momentum?

  1. Wave-particle duality

  2. Quantum superposition

  3. Quantum entanglement

  4. Quantum tunneling
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Wave-particle duality is the fundamental property of matter that it can exhibit both wave-like and particle-like behavior. In the context of quantum thermodynamics, wave-particle duality leads to the quantization of angular momentum.

Multiple choice

What is the primary mechanism responsible for quantum confinement effects in nanomaterials?

  1. Electron-electron interactions

  2. Electron-phonon interactions

  3. Confinement of electrons and holes in a small volume

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

Quantum confinement effects arise from the confinement of electrons and holes in a small volume, leading to discrete energy levels and unique electronic properties.

Multiple choice

The fundamental unit of electric charge is the:

  1. Electron

  2. Proton

  3. Neutron

  4. Quark

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

The fundamental unit of electric charge is the electron.

Multiple choice

What is the smallest unit of matter?

  1. Atom

  2. Molecule

  3. Electron

  4. Neutron
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An atom is the smallest unit of matter that retains all the chemical properties of an element.

Multiple choice

What is the role of computational modeling in the study of tokamak plasmas?

  1. To simulate plasma behavior and predict performance

  2. To design and optimize tokamak devices

  3. To analyze experimental data

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Computational modeling plays a vital role in the study of tokamak plasmas, as it allows us to simulate plasma behavior and predict performance, design and optimize tokamak devices, and analyze experimental data.

Multiple choice

What is the plasma frequency?

  1. The frequency at which plasma waves propagate

  2. The frequency at which ions oscillate in a magnetic field

  3. The frequency at which electrons oscillate in a magnetic field

  4. The frequency at which neutral atoms oscillate in a magnetic field
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The plasma frequency is the frequency at which plasma waves propagate. It is given by the following equation: ( f_p = \sqrt{\frac{n_e e^2}{m_e \varepsilon_0}} ), where ( n_e ) is the electron density, ( e ) is the elementary charge, ( m_e ) is the mass of the electron, and ( \varepsilon_0 ) is the permittivity of free space.

Multiple choice

What is the fundamental unit of matter?

  1. Atom

  2. Molecule

  3. Electron

  4. Neutron
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An atom is the fundamental unit of matter because it is the smallest unit that retains the chemical properties of an element.

Multiple choice

What is the basic unit of matter according to modern science?

  1. Atom

  2. Molecule

  3. Electron

  4. Neutron
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to modern science, the basic unit of matter is the atom, which is composed of a nucleus and electrons.