IB Physics HL E.1 Structure of the atom questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Question 1

Multiple choiceMedium1 mark

The schematic shows two spherical nuclei. Assume that all nucleons have the same mass. Each option gives RX/RYR_X/R_Y and ρX/ρY\rho_X/\rho_Y respectively. Which row is correct?

Nucleus Xnucleon number A=8RXNucleus Ynucleon number A=64RY
Show answer and explanation

Answer: C. The nuclear radius relation is R=R0A1/3R=R_0A^{1/3} From the figure, RX/RY=(8/64)1/3=1/2R_X/R_Y=(8/64)^{1/3}=1/2 The mass ratio is 1/81/8 and the spherical volume ratio is (1/2)3=1/8(1/2)^3=1/8 so ρX/ρY=(1/8)/(1/8)=1\rho_X/\rho_Y=(1/8)/(1/8)=1

A: uses the mass ratio as the density ratio, omitting the volume comparison.
B: reverses the radius ratio, although its density ratio is unity.
D: treats the masses as equal and uses the inverse volume ratio, giving 88
Remember: nuclear mass and volume both scale with nucleon number, so nuclear density is constant.

Question 2

Paper 2Medium7 marks

A gas is examined using an emission spectrum and an absorption spectrum. The absorption spectrum is recorded after continuous light passes through a cooler sample of the same gas. Figure 1 shows measured relative intensities for both spectra.

For calculations, use h=6.63×10−34 J sh=6.63\times10^{-34}\,\text{J s} and c=3.00×108 m s−1c=3.00\times10^8\,\text{m s}^{-1}

Emission spectrumAbsorption spectrum1.00.90.80.70.60.50.40.30.20.10.01.00.90.80.70.60.50.40.30.20.10.0400450500550600650670Relative emissionintensity /arbitrary unitsRelative absorptionintensity /arbitrary unitswavelength / nm
(a)

Read Figure 1 to state the wavelengths of the shortest- and longest-wavelength emission lines. Give your answers in nm.

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(b)

Determine the energy of a photon in the longest-wavelength emission line. Give your answer in J.

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(c)

Explain what the matching emission and absorption line positions indicate about atomic energy levels.

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(d)

A nucleus of the element contains 12 protons and 13 neutrons. Write its nuclear notation, using XX for the chemical symbol.

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