Mass number, atomic number and isotopes

There are different isotopes of the element lead.

What is the difference between the atoms of different isotopes of lead?

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The isotope lead-210 is radioactive.

What is meant by ‘lead-210 is radioactive’?

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The isotope lead-210 emits beta radiation.

What is beta radiation?

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The paint in an old painting contains the isotope lead-210.

The lead-210 in the paint can be used to estimate the age of the painting.

Figure 1 shows how the activity of the lead-210 in the paint changes with time.

What was the initial activity of the lead-210 in the paint?

Use Figure 1.

Calculate the activity of the lead-210 in the paint after one half-life.

What was the estimated age of the painting when the activity was 10 kBq?

Use Figure 1.

The paint also contains other radioactive substances.

A scientist removed the other radioactive substances before measuring the activity.

The activity would be greater if the other radioactive substances were not removed.

How would the estimate of the age of the painting be different if the activity was greater?

Use Figure 1.

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The other radioactive substances in the paint emit different types of radiation.

Complete the sentence.

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Complete the sentence.

Choose the answer from the box.

Some people used to think that radioactive substances had health benefits.

100 years ago, a company made toothpaste containing the radioactive isotopes radium-228 and radium-226.

Figure 3 shows the symbols for these isotopes.

How are atoms of radium-228 different from atoms of radium-226?

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Figure 4 shows how the activity of a sample of radium-228 changed over time.

What is the approximate half-life of radium-228?

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A scientist investigated whether the toothpaste in four tubes of the 100-year-old

toothpaste is equally radioactive.

Figure 5 shows the equipment used.

When the equipment was arranged as shown in Figure 5, it was not possible to detect alpha particles from the toothpaste.

Suggest how the scientist adjusted the equipment to detect alpha particles from the toothpaste.

The scientist adjusted the equipment and determined the activity of the toothpaste from each tube.

Table 1 shows the results.

What was the range of activities shown in Table 1 ?

What was the independent variable in the investigation?

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What was the dependent variable in the investigation?

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When the toothpaste was new, it caused a risk to health because of the nuclear radiation emitted.

What happened to the risk to health from the toothpaste after 100 years?

Which property makes nuclear radiation hazardous?

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Last century, scientists used evidence from the alpha particle scattering experiment to develop a new model of the atom.

In the experiment, alpha particles were directed towards a piece of gold foil.

What does an alpha particle consist of?

197 A gold atom has the symbol₇₉ Au.

How many neutrons are there in this gold atom?

The alpha particle scattering experiment led to the plum pudding model of the atom being replaced by the nuclear model.

Figure 11 shows the results predicted by the plum pudding model and the actual results from the alpha particle scattering experiment.

Describe how the actual results led to the plum pudding model of the atom being replaced by the nuclear model.

You should include details of the plum pudding model and the nuclear model of the atom.

Scientists did not know that neutrons existed when they first did alpha particle scattering experiments.

Which scientist did the experiments that provided evidence that neutrons exist?

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Last century, scientists used evidence from the alpha particle scattering experiment to develop a new model of the atom.

In the experiment, alpha particles were directed towards a piece of gold foil.

What does an alpha particle consist of?

197 A gold atom has the symbol₇₉ Au.

How many neutrons are there in this gold atom?

The alpha particle scattering experiment led to the plum pudding model of the atom being replaced by the nuclear model.

Figure 2 shows the results predicted by the plum pudding model and the actual results from the alpha particle scattering experiment.

Describe how the actual results led to the plum pudding model of the atom being replaced by the nuclear model.

You should include details of the plum pudding model and the nuclear model of the atom.

Scientists did not know that neutrons existed when they first did alpha particle scattering experiments.

Which scientist did the experiments that provided evidence that neutrons exist?

Tick () one box.

Protactinium (Pa) is radioactive.

An atom of one isotope of protactinium contains 91 protons and 143 neutrons.

What is the correct symbol for this atom?

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A teacher investigated how the count rate from a sample of protactinium changed over time.

Table 2 shows the results.

Figure 6 shows some of the teacher’s results.

Complete the graph in Figure 6.

Use data from Table 2.

Draw the line of best fit.

How much time did it take for the count rate to change from 200 counts per second to 100 counts per second?

What is the half-life of protactinium?

The nuclear radiation from the protactinium can pass through paper.

This radiation can only be detected up to 1 metre away from the protactinium.

What type of radiation is emitted by the protactinium?

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The teacher read an article about the effects of radiation on the human body.

Why are articles in scientific journals generally more trustworthy than articles in newspapers?

Radioactive nuclei can emit alpha, beta or gamma radiation.

Which type of radiation is the most penetrating?

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Which type of radiation is the most ionising?

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Which type of radiation has the longest range in air?

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When radioactive isotopes in the Earth’s crust decay they release energy.

The decay causes the heating of rocks in the crust.

Figure 8 shows the decay of uranium–238 (U–238) into thorium–234 (Th–234).

Figure 8

Complete Table 2 to show the number of neutrons and protons in the nuclei.

Geothermal power stations pump water through heated rocks.

The temperature of the water increases from 20 °C to its boiling point of 100 °C

Calculate the change in thermal energy when the mass of water heated is 150 kg

Specific heat capacity = 4 200 J/kg °C

Use the Physics Equations Sheet.

Figure 9 shows two models of the atom.

Write the labels on Figure 9

Choose the answers from the box.

Explain why the total positive charge in every atom of an element is always the same.

The results from the alpha particle scattering experiment led to the nuclear model.

Alpha particles were fired at a thin film of gold at a speed of 7% of the speed of light.

Determine the speed of the alpha particles.

Speed of light = 300 000 000 m/s

Figure 10 shows two atoms represented as solid spheres.

A hydrogen atom has a radius of 2.5 × 10^–11 m

Determine the radius of a magnesium atom.

Use measurements from Figure 10

Figure 1 shows two models of the atom.

Write the labels on Figure 1 Choose the answers from the box.

Explain why the total positive charge in every atom of an element is always the same.

The results from the alpha particle scattering experiment led to the nuclear model. Alpha particles were fired at a thin film of gold at a speed of 7% of the speed of light. Determine the speed of the alpha particles. Speed of light = 300 000 000 m/s

Figure 2 shows two atoms represented as solid spheres.

A hydrogen atom has a radius of 2.5 × 10^–11 m Determine the radius of a magnesium atom. Use measurements from Figure 2