Topic 5.1: Structure of the Atom Questions

A charged conducting ball carries a charge of +6.4 × 10⁻¹⁹ C.

Determine how many electrons have been removed from the ball.

(e = 1.60 × 10⁻¹⁹ C.)

State what is meant by saying that electric charge is quantised.

An ion contains 17 protons, 20 neutrons and 18 electrons.

What is the correct nuclear notation for this nuclide?

An alpha particle (charge +2e) is accelerated from rest through a potential difference of 1.5 × 10³ V between two parallel plates.

State, in electronvolts, the kinetic energy it gains.

State why the energy of an electron in an atom can only take certain values rather than any value at all.

Two nuclei are described as being isotopes of the same element.

Identify the quantity that must be the same for both nuclei, and the quantity that differs between them.

An electron is accelerated from rest through a potential difference of 250 V.

Define the electronvolt.

A neutral atom of an element has nucleon number 39 and proton number 19.

State the number of protons, neutrons and electrons in this atom.

An ion has 17 protons, 20 neutrons and 18 electrons.

Determine the nucleon number A, the overall charge of the ion, and hence write its nuclide symbol (the element with proton number 17 is chlorine, Cl).

Outline why the alpha-scattering experiment used a very thin metal foil and a source of fast alpha particles, rather than a thick foil or a beam of slow particles.

In the alpha-scattering experiment, a very small fraction of the alpha particles were repelled through angles greater than 90°, returning back towards the source.

Explain what this observation reveals about the size and charge of the nucleus.

A photon of light has an energy of 12.0 eV.

A charged oil drop is held stationary in a Millikan apparatus.

The charge on the drop is measured as 1.28 × 10⁻¹⁸ C.

An atom has four energy levels.

The downward transitions and the energy each one releases are: P releases 1.0 × 10⁻¹⁸ J, Q releases 6.0 × 10⁻¹⁹ J, R releases 2.5 × 10⁻¹⁹ J and S releases 8.0 × 10⁻¹⁹ J.

Identify which transition emits the photon with the longest wavelength, and explain your choice.

An electron in a hydrogen atom falls from a higher energy level to a lower one, emitting a photon of energy 1.9 eV.

A student claims that an atom of an element and a singly-charged positive ion of the same element 'are basically the same particle'.

Discuss this claim, identifying what stays the same and what changes between the neutral atom and its 1+ ion.

One step of the proton–proton fusion chain in the Sun releases about 0.42 MeV of energy.

Estimate this energy in joules.

A magnesium ion is represented by the nuclide notation with nucleon number 25 and proton number 12, carrying an overall charge of 2+.

State the number of protons, neutrons and electrons in this ion, and explain why the electron count differs from a neutral magnesium atom.

Outline how Millikan's oil-drop experiment provided evidence that electric charge is quantised.