Atomic Structure, particles, chargers and masses

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Atomic Structure, particles, chargers and masses — Free MYP5 Physics Practice Questions

1QuestionAtomic number (Z) and mass number (A)Concept Practice

3 marks~5 minCriterion A

The diagrams below show two simplified atomic models of carbon isotopes.

Diagram 1: nucleus with 6 protons and 6 neutrons; 6 electrons orbiting.
Diagram 2: nucleus with 6 protons and 7 neutrons; 6 electrons orbiting.

State the atomic number

Z

for both isotopes. [1]

Deduce the mass number

A

for each isotope and identify each diagram as carbon-12 or carbon-13. [1]

Explain why these two atoms are isotopes of the same element, despite having different mass numbers. [1]

Solutions

2QuestionDalton’s modelAssessment Practice

2 marks~3 minCriterion D

Dalton's atomic theory states that all atoms of a given element are identical in mass and properties.

Outline one real-world application of this assumption. [1]

Dalton's theory cannot fully account for the behaviour of chlorine in precise industrial chemical reactions. Discuss one limitation of his model that explains this, and state how it affects reaction accuracy. [1]

Solutions

3QuestionDalton’s modelAssessment Practice

5 marks~8 minCriterion C

A pure sample of element X is analysed. The graph below shows mass (in atomic mass units, u) versus number of atoms for this sample.

Graph data — Number of atoms (

\times 10^{23}

) : 0, 1, 2, 3, 4; Mass (u): 0, 20.18, 40.36, 60.54, 80.72

Deduce the average mass of one atom of element X from the graph. Show your working. [2]

Explain why Dalton's atomic model would predict an integer value for the mass per atom, and identify what feature of the graph contradicts this prediction. [1]

Analyse how the existence of isotopes modifies Dalton's model to account for the non-integer mass you calculated in (a). [2]

Solutions

4QuestionBohr model (energy levels)Assessment Practice

8 marks~12 minCriterion A

The Lyman series of hydrogen emission occurs when electrons fall to the ground state (

n = 1

). The first three lines have wavelengths:

n = 2 \to 1

121.6 \text{ nm}

n = 3 \to 1

102.6 \text{ nm}

n = 4 \to 1

97.3 \text{ nm}

A graph of

\dfrac{1}{\lambda}

(in

10^6 \text{ m}^{-1}

) against

\dfrac{1}{n^2}

(upper level) is plotted, giving a linear trend with

y

-intercept

1.097 \times 10^7 \text{ m}^{-1}

.

Use:

\dfrac{1}{\lambda} = R\!\left(\dfrac{1}{1^2} - \dfrac{1}{n^2}\right)

R = 1.097 \times 10^7 \text{ m}^{-1}

h = 6.63 \times 10^{-34} \text{ J s}

c = 3.00 \times 10^8 \text{ m s}^{-1}

1 \text{ eV} = 1.60 \times 10^{-19} \text{ J}

Explain why the series limit corresponds to the

y

-intercept of this graph. [2]

Deduce the series limit wavelength in nm. [3]

Evaluate the ionisation energy of hydrogen in eV using

E = hc/\lambda

, and assess the reliability of the experimental data by comparing your result with the accepted value of

13.6 \text{ eV}

. [3]

Solutions

5QuestionBohr model (energy levels)Assessment Practice

8 marks~12 minCriterion D

Technetium-99m (Tc-99m) is a radioactive isotope widely used in hospitals for imaging internal structures. It emits gamma radiation, detected by specialised cameras to diagnose conditions such as cancer. Tc-99m has a half-life of 6 hours. The energy of an emitted gamma photon is given by

E = hf

, where

h = 6.63 \times 10^{-34}

J s. Some patients require up to 3 scans per year throughout their lives.

Explain how a gamma photon is emitted from an excited Tc-99m nucleus, using the Bohr model of energy levels. [2]

A gamma photon emitted by Tc-99m has a frequency of

3.0 \times 10^{19}

Hz. Calculate the energy of this photon in joules. [2]

Evaluate the ethical justification for exposing a patient to repeated Tc-99m scans (3 per year). In your answer, state one assumption that underpins your evaluation. [4]

Solutions

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