Question 1

Which scientist proposed the “plum pudding” model of the atom, describing it as a sphere of positive charge with embedded electrons?

Accepted Answer

J.J. Thomson

Answer

Max Planck

Answer

Ernest Rutherford

Answer

Niels Bohr

Question 2

In Rutherford’s atomic model, what is the primary location of the positive charge in an atom?

Accepted Answer

Concentrated in a dense nucleus at the centre

Answer

Present only on the surface of the atom

Answer

Located in the electron shells surrounding thenucleus

Answer

Distributed uniformly throughout the atom

Question 3

Which of the following best describes a key improvement that Bohr’s atomic model made over Rutherford’s model?

Accepted Answer

It explained why atoms emit light at specific wavelengths (discrete spectral lines)

Answer

It demonstrated that the nucleus contains only protons

Answer

It proved that electrons have negligible mass

Answer

It showed that atoms are solid, indivisible spheres

Question 4

Thomson’s “plum pudding” model and Rutherford’s nuclear model both attempted to explain atomic structure. Which statement correctly identifies a major limitation of Thomson’s model that Rutherford’s model addressed?

Accepted Answer

Thomson’s model could not explain the existence and location of a nucleus

Answer

Thomson’s model failed to account for electron orbits around the nucleus

Answer

Thomson’s model suggested electrons were randomly distributed without any structure

Answer

Thomson’s model did not predict the overall stability of atoms

Question 5

Bohr’s atomic model successfully explained the hydrogen atom and predicted its emission spectrum accurately. However, it failed to explain the spectra of more complex atoms like helium or lithium. Which of the following best explains this limitation?

Accepted Answer

Bohr’s model assumed electrons occupy specific quantised energy levels, which works for single-electron atoms but fails for multi-electron atoms where electron-electron repulsion and orbital interactions become significant

Answer

Bohr’s model did not include a nucleus in its description of atomic structure

Answer

Bohr’s model was based on incorrect measurements of electron mass and charge

Answer

Bohr’s model assumed all atoms have the same numberof electrons regardless of atomic number

Question 6

What is meant by the “ground state” of an electron in an atom?

Accepted Answer

The lowest energy level (n = 1) where the electron is closest to the nucleus

Answer

Any energy level above n = 1 where the electronis in an excited state

Answer

The state when an electron has been ionised and removed from the atom

Answer

The state when an electron absorbs a photon and moves to a higher energy level

Question 7

Calculate the energy of a photon of frequency f = 5.0 ×10¹⁴ Hz. (Planck’s constant, h = 6.63 × 10⁻³⁴ J·s)

Accepted Answer

3.3 × 10⁻¹⁹ J

Answer

3.3 × 10⁻⁴⁷ J

Answer

3.3 × 10⁻⁴⁸ J

Answer

7.5 × 10⁻²⁰ J

Question 8

A photon with a wavelength of 400 nm (violet light) is absorbed by an atom. Which statement best describes what happens when this photon is absorbed? (h = 6.63 × 10⁻³⁴ J·s, c = 3.00 × 10⁸ m/s)

Accepted Answer

The photon energy is approximately 5.0 × 10⁻¹⁹J, which is sufficient to excite an electron to a higher energy level

Answer

The photon energy cannot be determined without knowing the specific type of atom

Answer

The photon energy is approximately 1.2 × 10⁻²⁵J, which is too small to affect the electron

Answer

The photon energy is approximately 5.0 × 10⁻¹⁹J, which is sufficient to ionise the atom completely

Question 9

When electrons in a hydrogen atom transition from different excited states to the ground state, different coloured light is emitted. For example, a transition from n = 3 to n = 1 emits ultraviolet light, while a transition from n = 2 to n = 1 emits red light. Which of the following best explains why different colours are emitted?

Accepted Answer

Different transitions release different amounts of energy, corresponding to different photon frequencies and thus different colours of light

Answer

The wavelength of emitted light is independent of the energy released during the transition

Answer

All transitions release the same amount of energy regardless of the initial and final energy levels

Answer

The nucleus emits different colours of light depending on the total number of electrons in the atom

Question 10

An electron in a hydrogen atom transitions from the first excited state (n = 2) to the ground state (n = 1). Which of the following correctly describes what occurs during this transition?

Accepted Answer

The atom emits a photon with energy equal to the energy difference between the two levels

Answer

No energy change occurs because the electron remains in the atom

Answer

The atom absorbs a photon with energy equal to the energy difference between the two levels

Answer

The electron gains kinetic energy and moves faster around the nucleus

Question 11

Which atomic model proposed that the atom consists of a sphere of positive charge with embedded negative electrons?

Accepted Answer

J.J. Thomson’s “plum pudding” model

Answer

Ernest Rutherford’s nuclear model

Answer

The quantum mechanical model

Answer

Niels Bohr’s model

Question 12

What does the term “ground state” refer to in atomic physics?

Accepted Answer

The state when an electron is in its most stable position closest to the nucleus

Answer

The state when an electron is ionised from the atom

Answer

The state when an electron is in the second energy level

Answer

The state when an electron has absorbed maximumenergy

Question 13

Which of the following is the correct equation relating photon energy to frequency?

Accepted Answer

E = hf

Answer

E = h/λ

Answer

E = hc/λ

Answer

E = λf

Question 14

What is the value of Planck’s constant (h)?

Accepted Answer

6.63 × 10⁻³⁴ Js

Answer

1.38 × 10⁻²³ J K⁻¹

Answer

1.602 × 10⁻¹⁹ J

Answer

3.00 × 10⁸ m s⁻¹

Question 15

What does “quantised energy levels” mean in Bohr’s atomic model?

Accepted Answer

Electrons can only exist in specific orbits with discrete energy values

Answer

Electrons have the same energy regardless of their position

Answer

Electrons move continuously around the nucleus

Answer

Electrons can exist at any distance from the nucleus

Question 16

Which scientist proposed the nuclear model of the atom, suggesting a dense, positively charged nucleus surrounded by orbiting electrons?

Accepted Answer

Ernest Rutherford

Answer

Max Planck

Answer

J.J. Thomson

Answer

Niels Bohr

Question 17

What is the value of speed of light in vacuum (c) used in photon energy calculations?

Accepted Answer

3.00 × 10⁸ m s⁻¹

Answer

5.00 × 10¹⁴ m s⁻¹

Answer

6.63 × 10⁻³⁴ m s⁻¹

Answer

1.602 × 10⁻¹⁹ m s⁻¹

Question 18

Which of the following best describes the main limitation of Rutherford’s atomic model?

Accepted Answer

It did not explain the exact positions of electrons or the stability of atoms

Answer

It only worked for atoms with one electron

Answer

It failed to explain the existence of the nucleus

Answer

It suggested electrons were embedded in positive charge

Question 19

What is the key difference between the “ground state” and an “excited state” of an electron?

Accepted Answer

Ground state electrons are at the lowest energy level; excited state electrons are at higher energy levels

Answer

Ground state electrons are found in the nucleus; excited state electrons orbit the nucleus

Answer

Ground state electrons emit photons; excited state electrons absorb photons

Answer

Ground state electrons are ionised; excited state electrons are bound to the nucleus

Question 20

Calculate the energy of a photon with wavelength λ = 4.0 × 10⁻⁷ m. (Use h = 6.63 × 10⁻³⁴ Js and c = 3.00 × 10⁸ m s⁻¹)

Accepted Answer

4.97 × 10⁻¹⁹ J

Answer

1.33 × 10⁻¹⁸ J

Answer

4.97 × 10⁻²⁰ J

Answer

8.84 × 10⁻²⁶ J

Question 21

Which of the following correctly compares Thomson’s and Rutherford’s atomic models?

Accepted Answer

Thomson’s model described electrons embedded in positive charge; Rutherford’s model described a nucleus with orbiting electrons

Answer

Rutherford’s model was developed before Thomson’s model

Answer

Thomson’s model included a nucleus; Rutherford’s model did not

Answer

Both models successfully explained atomic stability

Question 22

Rutherford’s model improved upon Thomson’s model by explaining the nucleus, but it could not explain why electrons do not collapse into the nucleus due to electrostatic attraction. Which of the following best explains why Bohr’s model addressed this limitation?

Accepted Answer

Bohr introduced quantised energy levels, suggesting electrons can only occupy specific stable orbits without radiating energy

Answer

Bohr suggested that electrons are held in place by strong nuclear forces

Answer

Bohr proposed that electrons move in straight lines away from the nucleus

Answer

Bohr eliminated the concept of the nucleus entirely

Question 23

An electron in a hydrogen atom absorbs a photon and transitions from n = 1 to n = 3. Later, it returns to n = 1 by first transitioning to n = 2, then from n = 2 to n = 1. Which statement correctly compares the photons emitted in these two transitions?

Accepted Answer

The single photon emitted when going directly from n = 3 to n = 1 has the same energy as the sum of the two photons emitted in the two-step transition

Answer

The single photon emitted when going directly from n = 3 to n = 1 has more energy than the sum of the two photons emitted in the two-step transition

Answer

The energy of photons emitted is independent of the transition pathway

Answer

The single photon emitted when going directly from n = 3 to n = 1 has less energy than the sum of the two photons emitted in the two-step transition

Question 24

A photon with wavelength λ = 5.0 × 10⁻⁷ m is emitted during an electron transition. Calculate the energy of this photon and explain what this energy represents in the context of atomic transitions. (h = 6.63 × 10⁻³⁴ Js, c = 3.00 × 10⁸ m s⁻¹)

Accepted Answer

3.98 × 10⁻¹⁹ J; this represents the energy difference between two specific energy levels in the atom

Answer

8.38 × 10⁻²⁶ J; this represents the kinetic energy of the electron

Answer

3.98 × 10⁻¹⁹ J; this represents the total energy of the atom

Answer

1.20 × 10⁻¹⁸ J; this represents the ionisation energy of the atom

Question 25

Consider the following statement: “Bohr’s model successfully explained the spectrum of hydrogen but failed to accurately predict the spectra of more complex atoms like helium.” Which of the following best explains why Bohr’s model has this limitation?

Accepted Answer

Bohr’s model only accounts for single-electron atoms, where the electron experiences a simple Coulomb force from the nucleus; in multi-electron atoms, electron-electron repulsion and shielding effects complicate the energy levels in ways Bohr’s model cannot predict

Answer

Complex atoms have more neutrons, which Bohr’s model did not account for

Answer

Bohr’s model was designed specifically for helium and does not work for hydrogen

Answer

Bohr’s model assumes electrons are particles, but in complex atoms they behave as waves

Question 26

A scientist observes that an atom emits light of a specific wavelength when an electron transitions between two energy levels. Based on this observation, which of the following can be inferred about the atomic structure?

Accepted Answer

The energy difference between the two levels is directly related to the wavelength of the emitted light, and this relationship supports the quantised energy level model proposed by Bohr

Answer

The atom has only two energy levels

Answer

The wavelength of light is independent of the energy levels involved in the transition

Answer

The atom is unstable and will decay

Question 27

Which of the following particles is found in the nucleus of an atom?

Accepted Answer

Proton

Answer

Positron

Answer

Electron

Answer

Photon

Question 28

If an atom has 8 protons and 8 neutrons, what is itsmass number?

Accepted Answer

16

Answer

8

Answer

4

Answer

0

Question 29

Which of the following pairs represents isotopes of the same element?

A) Carbon-12 and Nitrogen-14

B) Carbon-12 and Carbon-14

C) Oxygen-16 and Oxygen-18

D) Both B and C

Accepted Answer

Both B and C

Answer

B only

Answer

C only

Answer

A only

Question 30

The strong nuclear force in the nucleus is primarily responsible for:

Accepted Answer

Holding protons and neutrons together

Answer

Repelling electrons from the nucleus

Answer

Producing radioactive decay

Answer

Creating the electron shells

Question 31

An atom of Uranium-235 has 92 protons. How many neutrons does it have?

Accepted Answer

143

Answer

235

Answer

92

Answer

327

Question 32

Which of the following factors does NOT influence radioactive decay?

Accepted Answer

All of the options do not influence radioactive decay

Answer

Chemical changes

Answer

Pressure

Answer

Temperature

Question 33

Which statement best explains why radioactivity poses potential hazards to living organisms?

Accepted Answer

Radiation can damage cells and DNA if not properly shielded against

Answer

Radioactivity only affects metals

Answer

Radioactive materials are always visible to the naked eye

Answer

Radioactive decay only occurs in laboratories

Question 34

Which of the following is a medical application of radioactivity?

A. Treatment of certain cancers using beta particles

B. Imaging techniques using radioactive tracers

C. Nuclear energy production

D. Both A and B

Accepted Answer

D

Answer

B only

Answer

C only

Answer

A only

Question 35

Which type of radiation requires dense materials such as lead or concrete for effective shielding?

Accepted Answer

Gamma radiation

Answer

Beta radiation

Answer

Alpha, Beta and Gamma radiations

Answer

Alpha radiation

Question 36

Gamma decay differs from alpha and beta decay because:

Accepted Answer

It does not change the number of protons or neutrons in the nucleus

Answer

It produces a positron instead of an electron

Answer

It always occurs before alpha decay

Answer

It involves the emission of a helium nucleus

Question 37

In beta-minus decay, the atomic number of thenucleus:

Accepted Answer

Increases by 1

Answer

Remains unchanged

Answer

Increases by 2

Answer

Decreases by 1

Question 38

Beta-minus (β⁻) decay occurs when:

Accepted Answer

A neutron is converted into a proton

Answer

An electron is absorbed by the nucleus

Answer

A proton is converted into a neutron

Answer

A photon is emitted from the nucleus

Question 39

Which type of radiation has the lowest penetrationpower?

Accepted Answer

Alpha radiation

Answer

Position

Answer

Gamma radiation

Answer

Beta radiation

Question 40

When an atom undergoes alpha decay, its mass number:

Accepted Answer

Decreases by 4

Answer

Decreases by 2

Answer

Increases by 4

Answer

Remains unchanged

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