Topic 5.1: Structure of the Atom Questions

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.

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.

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.)

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 what is meant by saying that electric charge is quantised.

Define the electronvolt.

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

A cool gas placed in front of a continuous white-light source produces an absorption spectrum, while the same gas when heated produces an emission spectrum.

Describe how the appearance of these two spectra differs.

In the Geiger-Marsden (alpha-scattering) experiment, a beam of alpha particles is directed at a thin gold foil.

Describe two observations of the alpha particles' paths, and outline how these observations were interpreted in terms of the structure of the atom.

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

An isolated atom of a certain gas has only three energy levels. When the gas is excited, its emission spectrum contains exactly three spectral lines, corresponding to emitted photon energies of 1.0 eV, 2.0 eV and 3.0 eV.

Which set of atomic energy levels (measured upward from the ground state) is consistent with this emission spectrum?

An atom has four energy levels, with energies measured relative to the ionised state:

n = 4: −1.0 eV
n = 3: −2.0 eV
n = 2: −4.0 eV
n = 1: −9.0 eV

The atom can emit a photon when an electron drops between two of these levels. Which transition produces the photon with the longest wavelength?

A student writes: 'To change a photon energy from joules into electronvolts, multiply by 1.60 × 10⁻¹⁹.' Explain why this statement is wrong and state the correct rule.

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.

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

Estimate this energy in joules.

Electrons in a sample of atoms are excited to the fifth energy level (n = 5).

Determine the maximum number of different wavelengths that can appear in the emission spectrum as the electrons return to the ground state by every possible route.

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.

An electron in an atom moves from an energy level of −1.5 eV to a level of −6.0 eV, emitting a photon.