Structure of the Atom (DP IB Physics: SL): Exam Questions

In a HeNe laser, electrons collide with helium atoms. The ground state of a helium is labelled as 1s and the next energy level is labelled 2s.

When an electrons de-excite from 2s to 1s in helium, photons are emitted with a wavelength of 58.4 nm.

Calculate the energy difference of this transition, giving your answer in eV.

An electron collides with a helium in its ground state, causing an electron to transition from 1s to 2s. The electron initially has 45.0 eV of kinetic energy.

Calculate the electron’s kinetic energy after the collision.

Explain why it is not possible for the same electron from (b) to collide with the ground state helium atom and be left with 40.0 eV of kinetic energy. 

Helium and neon coincidentally have very similar energy gaps for certain transitions, allowing one atom to cause an excitation in the other.

The excited helium atom from part (b) then collides with a ground state neon atom. The neon atom becomes excited and subsequently emits two photons in order to return to its ground state.

(i) If the helium is left back in its ground state after the collision, determine the amount of energy transferred to the neon atom.

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(ii) If one photon has an energy of 1.96 eV, calculate the wavelength of the other.

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Rutherford used the scattering of α particles to provide evidence for the structure of the atom. The apparatus includes a narrow beam of α particles fired at a very thin sheet of gold foil inside a vacuum chamber.

Explain why it is essential to use:

(i) a vacuum in the chamber

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(ii) a very thin sheet of gold foil    

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(iii) a narrow beam of alpha particles   

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The diagram shows α particles incident on a layer of atoms in a gold foil.

On the diagram, draw the paths followed by each of the incident α particles shown.

Outline the results of the scattering experiment by explaining:

(i) the main observations of the scattering experiment

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(ii) the significance of each observation

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The Thomson model of the atom preceded Rutherford’s model. In the Thomson model, the atom was imagined as a sphere of positive charge of diameter 10^–10 m containing electrons moving within the sphere.

Thomson’s model could explain some of the results of the Rutherford experiment, but not all.

Explain

(i) why, at small deflections, Rutherford’s experiment can be explained by Thomson’s model but not at large deflections

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(ii) why Rutherford’s model of the atom can account for the results at both small and large deflections

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The lowest energy levels of an argon atom are shown below. 

Calculate the wavelength of an emitted photon due to the transition level n = 5 to level n = 3.

Draw arrows on the diagram above to show the electron transitions which emit a photon with a longer wavelength than that emitted in the transition from n = 5 to n = 3. 

A fluorescent tube is filled with argon gas at low pressure. When the argon atoms are excited, they emit photons.

Explain how the excited argon atoms emit photons.

Explain how the coating on the inside surface of the glass in a fluorescent tube helps to emit photons in the visible spectrum.

Two students debate which electron energy transition causes a photon of infrared radiation to be emitted from excited hydrogen atoms. 

Student 1 thinks it’s the transition to  .

Student 2 thinks it’s the transition  to .

State and explain which student is correct.

In a new type of special effects tube covered in a special infrared absorbent coating, the hydrogen atoms inside are excited. This leads to a series of events which result in the emission of photons in the visible region of the electromagnetic spectrum from the coating of the tube. 

Describe the series of events, following the excitation of the atoms, which results in the emission of visible photons.

Discuss the meaning of the first molar ionisation energy.

Transitions between three energy levels in a particular atom give rise to three spectral lines. In decreasing magnitudes, these are , and .

The equation which relates , and  is:

Explain, including through the use of a sketch, how this equation relates ,  and .

A different atom has a complete line emission spectra with a ground state energy of  –10.0 eV. is:

Sketch and label a diagram of the possible energy levels for the atomic line spectra shown.

Explain the significance of an electron at an energy level of 0 eV.

(i) Explain the statement 'the first excitation energy of the hydrogen atom is 10.2 eV'

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(ii) The ground state of hydrogen is –13.6 eV. Calculate the speed of the slowest electron that could cause this excitation of a hydrogen atom. 

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