Atoms & Isotopes Practice Questions

Which of the following is the approximate radius of an atom?

Tick (✓) one box.

• $1 \times 10^{-15}$ m
• $1 \times 10^{-10}$ m
• $1 \times 10^{-6}$ m
• $1 \times 10^{-3}$ m

The table gives information about the particles in an atom.

Complete the table.

Particle	Relative charge	Where it is found in the atom
Proton	$+1$	in the nucleus
Neutron		in the nucleus
Electron

The radius of a nucleus is less than $\dfrac{1}{10\,000}$ of the radius of an atom.

Estimate the radius of a nucleus. Give your answer in standard form.

How many neutrons are there in a nucleus of atom D?

How many electrons are there in a neutral atom of A?

Which two atoms in the table are isotopes of the same element?

Tick (✓) one box.

• A and B
• B and C
• C and D
• D and E

What were atoms thought to be before the discovery of the electron?

The discovery of the electron led to the plum pudding model.

Describe the plum pudding model of the atom.

What is meant by isotopes?

Complete the table for a neutral atom of each isotope.

	Chlorine-35	Chlorine-37
Number of protons	17	17
Number of neutrons
Number of electrons

Explain why an atom of chlorine-37 has no overall electrical charge.

Most of the alpha particles followed a path like particle A.

What does this show about the structure of the atom?

A very small number of alpha particles followed a path like particle C.

Explain what this shows about the nucleus of a gold atom.

Suggest one reason why the experiment had to be carried out in a vacuum.

Where are the electrons found in an atom?

An electron in a sodium atom absorbs electromagnetic radiation.

Describe what happens to the position of this electron.

Explain, in terms of energy levels, how the atoms in the lamp give out orange light.

State the number of electrons in a neutral lithium atom and explain why the atom has no overall charge.

The lithium atom loses one outer electron.

Give the charge on the ion that is formed and explain your answer.

A magnesium ion is represented as $^{24}_{12}\text{Mg}^{2+}$.

Determine the number of protons, neutrons and electrons in this ion.

Name the scientist whose experimental work provided the evidence for the existence of neutrons.

Describe how Niels Bohr adapted the nuclear model, and state why his idea was accepted by other scientists.

Evidence for the neutron was found about 20 years after the nucleus became an accepted scientific idea.

Explain what this tells us about how scientific models are developed.

Calculate how many times greater the radius of the atom is than the radius of the nucleus.

The volume of a sphere is proportional to the cube of its radius.

Calculate how many times greater the volume of the atom is than the volume of the nucleus.

Give your answer in standard form to 2 significant figures.

The nucleus takes up only a tiny fraction of the volume of the atom.

Explain why almost all of the mass of the atom is still concentrated in the nucleus.

In 1904 the plum pudding model was used to describe the atom. A few years later, the results of the alpha particle scattering experiment led scientists to replace it with the nuclear model.

Describe the plum pudding model, and explain how the results of the alpha particle scattering experiment led to the nuclear model replacing it.

[6 marks]