Radioactivity Summary Notes

What is a positron?

The antimatter particle of the electron.

Who proposed the Plum Pudding Model?

J.J. Thomson in 1904.

What does the Plum Pudding Model suggest about the atom?

It is a sphere of positive charge with negatively charged electrons dotted inside.

What experiment did Rutherford conduct in 1914?

He bombarded thin gold foil sheets with alpha particles.

What was the expected outcome of Rutherford's experiment?

Nearly all alpha particles would pass through the foil with only a few deflected at small angles.

What were the actual observations from Rutherford's experiment?

Most alpha particles passed through, a few were deflected by the nucleus, and very few were deflected by large angles.

What conclusion can be drawn from Rutherford's experiment?

Atoms are mainly empty space and have a small, positively charged nucleus.

What are nucleons?

Protons and neutrons that make up the nucleus.

What is the relative charge of a proton?

Positive.

What is the mass number in atomic notation?

The sum of protons and neutrons.

What is an isotope?

An atom of the same element with a different number of neutrons.

What is the main idea of Bohr's model?

Electrons orbit the nucleus at different distances, called energy levels.

What happens when an electron moves between energy levels?

It absorbs or emits electromagnetic radiation.

What is nuclear radiation?

Radiation that occurs in the nucleus of an unstable atom.

How can nuclear radiation be detected?

Using photographic film or a Geiger-Müller counter.

What is ionising radiation?

Radiation that removes electrons from atoms, creating positive ions.

What are the main types of nuclear radiation?

Alpha, beta-minus, beta-plus, gamma, and neutron radiation.

What is alpha radiation composed of?

2 protons and 2 neutrons, essentially helium nuclei.

How does beta-minus decay occur?

A neutron decays into a proton and emits an electron.

How does beta-plus decay occur?

A proton decays into a neutron and emits a positron.

What does gamma radiation do?

Emits electromagnetic radiation to stabilize the nucleus.

What is the definition of half-life?

The average time taken for half of the radioactive nuclei in a sample to decay.

What happens to the activity of a radioactive sample over time?

It decreases as there are fewer unstable nuclei remaining.

What are common sources of background radiation?

Radon gas, cosmic rays, ground materials, food, and medical sources.

How does radon gas contribute to background radiation?

It is an alpha source that is dangerous when inhaled.

What type of radiation is emitted from high altitude exposure?

Cosmic rays.

What is the unit for measuring radioactive activity?

Becquerel.

What is the role of radioactive isotopes in medical applications?

They are used for treatment and diagnosis.

What is the danger of alpha radiation when ingested?

It can be very harmful, as it is highly ionising.

What occurs during alpha decay?

The ejection of 2 protons and 2 neutrons from an unstable nucleus.

What is the consequence of a neutron decay in beta-minus?

A new element is created with one more proton.