The structure of an atom

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?

Tick (✓) one box.

The camera in a mobile phone uses an LED to provide light when taking a photograph. A student investigated how the potential difference across an LED varies with the current in it. Figure 9 shows the circuit used.

The student closed the switch. The voltmeter gave a reading of 5.0 V The ammeter gave a reading of 0 mA The LED did not emit any light. Explain how the student should have changed the circuit to make the LED emit light.

The student changed the circuit so that the LED emitted light. The current in the circuit was 290 mA The power of the LED was 0.98 W Calculate the potential difference across the LED. Use the Physics Equations Sheet. Give your answer to 2 significant figures.

A traditional camera uses a flash unit to provide light. Figure 10 shows a flash unit on a traditional camera.

The flash unit emits light from xenon gas in a fluorescent tube. What happens when a xenon atom emits light? Tick (✓) one box.

When the flash unit is used there is a mean potential difference of 200 V across the fluorescent tube. The flash of light lasts for 2.8 × 10^–4 s 1.4 J of energy is transferred. Calculate the mean current. Use the Physics Equations Sheet.

A radioactive source emits alpha, beta and gamma radiation.

An alpha particle is the same as a helium nucleus.

How many times bigger is the radius of a helium atom than the radius of an alpha particle?

Tick (✓) one box.

Alpha particles can ionise atoms in the air.

What happens to an atom when it is ionised by an alpha particle?

Tick (✓) two boxes.

A spark detector is a device that can be used to detect alpha radiation.

A spark detector works by alpha particles ionising atoms in the air near a wire mesh.

A large potential difference creates a spark when the air near the wire mesh is ionised.

Suggest why a spark detector cannot detect beta radiation.

A teacher wants to demonstrate that the radioactive source emits alpha, beta and gamma radiation.

Figure 11 shows the equipment the teacher has.

Describe a method the teacher could use.

A radioactive source emits alpha, beta and gamma radiation.

An alpha particle is the same as a helium nucleus. How many times bigger is the radius of a helium atom than the radius of an alpha particle? Tick (✓) one box.

Alpha particles can ionise atoms in the air. What happens to an atom when it is ionised by an alpha particle? Tick (✓) two boxes.

A spark detector is a device that can be used to detect alpha radiation. A spark detector works by alpha particles ionising atoms in the air near a wire mesh. A large potential difference creates a spark when the air near the wire mesh is ionised. Suggest why a spark detector cannot detect beta radiation.

A teacher wants to demonstrate that the radioactive source emits alpha, beta and gamma radiation. Figure 3 shows the equipment the teacher has.

Describe a method the teacher could use.

In an experiment, a beam of alpha particles was directed at a thin sheet of gold foil.

Most of the alpha particles passed straight through the gold foil.

Alpha particles which passed close to the nucleus of a gold atom did not pass straight through.

What happened to the alpha particles which passed close to the nucleus of a gold atom?

The results suggested that the diameter of the nucleus of a gold atom is of the 0 3. 2 diameter of the atom.

The diameter of a gold atom is 0.18 nm

Calculate the diameter of a gold nucleus in nm

Further experiments showed that gold nuclei are surrounded by electrons in different energy levels.

Figure 4 shows three of the energy levels around the nucleus of a gold atom.

The electron in energy level B absorbs electromagnetic radiation.

Which energy level will the electron be in after it has absorbed the electromagnetic radiation?

Tick (✓) one box.

Figure 5 shows how the temperature of a small sample of gold changes as it is heated from a solid to a liquid.

What is the melting point of the gold?

How many minutes did it take for all of the gold in the sample to change from solid to liquid?

What does the gradient of the graph in Figure 5 represent?

Tick (✓) one box.

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