KS4: Radioactivity

What are the components of an atom?

An atom consists of a positively charged nucleus made of protons and neutrons, surrounded by negatively charged electrons.

What is the atomic number of an element?

The atomic number is the number of protons in the nucleus of an atom of that element.

What is a mass number?

The mass number is the total number of protons and neutrons in an atom.

What are isotopes?

Isotopes are atoms of the same element that have different numbers of neutrons.

What happens when an atom loses outer electrons?

It turns into positive ions if it loses one or more outer electron(s).

What is radioactive decay?

Radioactive decay is the random process by which unstable atomic nuclei lose energy by emitting radiation.

How is activity measured?

Activity is measured in becquerel (Bq). 1 decay per second.

What is a half-life?

The half-life of a radioactive isotope is the time it takes for the number of nuclei in a sample to halve.

What is the difference between contamination and irradiation?

Radioactive contamination is the unwanted presence of radioactive materials, while irradiation is the exposure of an object to nuclear radiation without it becoming radioactive and it has a strong ionising power with a range of 10-20cm and a low penetrating power(blocked by paper). It also has little deflection in a magnetic/electric field because it has charge.

What does alpha decay produce?

Alpha decay produces an alpha particle, which consists of two neutrons and two protons.

What type of particle does beta decay emit?

Beta decay emits a high-speed electron as a neutron turns into a proton. It has a medium ionising power with a range of 1m and a medium penetrating power(blocked by 2cm of aluminium). It does deflect in the opposite direction of the alpha particle when in an electric or magnetic field.

What is a gamma ray?

A gamma ray is electromagnetic radiation emitted from the nucleus. It has a weak ionising power and an infinite range in air. It has a high penetrating power(blocked by few cm of lead) and it has no deflection in an electric or magnetic field as it has no charge.

What is background radiation?

Background radiation is the radiation we are exposed to on a daily basis.

What is nuclear fission?

Nuclear fission is the splitting of a large and unstable nucleus into two smaller nuclei.

What initiates the fission process?

For fission to occur, an unstable nucleus must first absorb a neutron.

What is a chain reaction in nuclear fission?

A chain reaction occurs when neutrons released from fission events go on to induce further fissions.

What is nuclear fusion?

Nuclear fusion is the process of combining two light nuclei to form a heavier nucleus. It is only possible under extreme condition(very high temperature and pressure) which cause the nuclei to overcome their repulsion and fuse to release vast amounts of energy. You need to fuse hydrogen(deuterium) with hydrogen 3/tritium but there is little supply of tritium and hydrogen 3 on earth. The conditions needed are also expensive to obtain.

Why do hazards associated with radioactive materials differ?

Hazards differ according to the half-life involved, affecting how long the radiation persists.

What is an example of a man-made source of background radiation?

Medical radiation from x rays.

How is radiation dose measured?

Radiation dose is measured in sieverts (Sv). 1 Joule per kilogram.

How do alpha particles affect the mass and charge of a nucleus?

The mass number would decrease by 4 and the number of protons would decrease by 2 resulting in a new element, as an alpha particle is 2 protons and 2 neutrons.

How does beta decay affect the mass and charge of a nucleus?

Beta decay does not change the mass but increases the charge of the nucleus and increases the number of protons by 1.

How do gamma rays affect the mass and charge of a nucleus?

The emission of gamma rays does not alter the number of protons or neutrons in the nucleus but instead has the effect of moving the nucleus from a higher to lower energy state(unstable to stable).

What can lead to a change in scientific models?

New experimental evidence may lead to changes or replacements of scientific models.

Why would an airplane pilot have a higher average annual radiation does?

The atmosphere is thinner at a high altitude which means that they are exposed to more cosmic rays.

Why is gamma used as a tracer in the body?

It is able to escape the human body and be detected externally, allowing for imaging without invasive procedures.

What happens to the structure of an atom when it is ionised?

If the atom becomes ionised the number of electrons will change.

What happens when control rods are lowered into a reactor?

They absorb neutrons produced from nuclear fission and this causes the chain reaction to slow/stop and less energy is released.

Who was Democritus?

Democritus was a Greek philosopher in 400 BCE and invented the thought experiment that matter is made up of indivisible spheres called atoma.

Who was John Dalton?

He was a scientist who discovered that all matter was made up of tiny particles called atoms(indivisible spheres) in 1803.

Who was JJ Thomson?

JJ Thomson discovered the electron in 1897, and created the plum pudding model which was a positive cloud(pudding) with negative electrons embedded in it(pudding).

Who was Ernest Rutherford?

He created the nuclear model(mass of atom concentrated in small, positive nucleus with most of the atom being empty space), disproving the plum pudding model. He also discovered the proton in 1919, by binding alpha particles with nitrogen nuclei and it created a fluorine nucleus that was too proton rich causing a proton to be ejected from the nucleus which was then detected, identified and named by Rutherford.

What was the golden foil experiment?

An experiment was carried out to direct alpha particles at a thin gold foil. The plum pudding model suggested that mass and charge were evenly spread throughout the atom. It was expected that the particles would be scattered evenly by the atoms. It was found that most alpha particles passed straight through the foil meaning most of the atom is empty space. A few alpha particles were deflected through large angles, meaning the atoms have a small, dense, positive nucleus.

Who was Niels Bohr?

He discovered that the electrons orbit the nucleus on shells. When an electron moves down an energy level it will emit a specific wavelength of light. An electron can also absorb a specific wavelength of light to move up an energy level.

Who was James Chadwick?

He discovered the neutron in 1932. Chadwick used a version of Rutherford's experiment, using a sheet of beryllium and a paraffin block instead of gold foil. He was able to prove that a proton-sized neutral particle - now known as the neutron - existed.

Name a use of beta decay.

Beta can be used to monitor the thickness of aluminium. A beta emitter shoots beta particles through the thin aluminium and a detector detects the amount of beta. If the amount is too low or too high, the rollers adjust.

What is carbon dating?

Carbon dating is a scientific method used to determine the age of an artifact or organic material by measuring the amount of carbon-14 it contains and using half life of carbon 14(600 years) to calculate the age of the material.

How is gamma used for sterilisation?

Gamma radiation is used for sterilization by effectively killing bacteria, viruses, and other pathogens on medical equipment and supplies. This method ensures that the items are free from contaminants without compromising their integrity. It penetrates materials, allowing it to sanitize without heat.

How are alpha particles used in smoke detectors?

Alpha particles ionise the air, creating a current and when smoke gets in the way and absorbs alpha particles, the current decreases, triggering the alarm.

How is gamma used in radiotherapy?

Low doses of gamma are shot from different directions, so that there is a high dose concentrated at the cancer to kill it, but lower doses around the cancer to not harm the body.

How does a nuclear power station work?

Fission is in the core and it generates heat energy, which boils water and produces steam to turn a turbine and generate electricity. Control rods absorb the neutrons to regulate the fission process and maintain a safe reaction rate.