Radioactivity

When an atom’s unstable nucleus decays, a nuclear transformation occurs and stabilizes the nucleus. This process is accompanied by one or more types of radiation: alpha radiation |(\alpha),| beta radiation |(\beta)| and gamma radiation |(\gamma).|

Radioactivity has various applications and impacts, such as dating ancient objects, generating energy, developing medical treatments and more. Evaluating an atom’s half-life can reveal its ability to decay and how this decay can be used.

While alpha |(\alpha)| and beta |(\beta)| radiation are forms of particle radiation, gamma radiation |(\gamma)| is electromagnetic. These properties influence the ability of the radiation to penetrate matter. For instance, gamma |(\gamma)| radiation has greater penetration capacity than alpha |(\alpha)| and beta |(\beta)| particles. Smaller and lighter beta particles |(\beta)| have greater penetration capacity than alpha particles |(\alpha).|

The following diagram shows the penetration capacity of different types of radiation.

These three types of radiation carry a lot of energy. When penetrating matter, they can create ions, which is why they are also known as ionizing radiation. This can be beneficial or dangerous to human health, depending on how the exposure occurs.

It also indicates the stability of an isotope.

In a highly unstable isotope, it takes very little time for half of the atoms in a sample to decay, so the half-life is short. For example, bohrium-271 |(^{271}\text{Bh})| is very unstable, with a half-life of just |1.2| seconds.

In a highly stable isotope, it takes much more time for half of the atoms in a sample to decay, so the half-life is long. For example, iodine-129  |(^{129}\text{I})| has a half-life of |15.7| million years.

The half-life concept can also be used to date archaeological specimens using carbon, uranium and even lead.

Alpha particles |(\alpha)| can be represented in various ways.

Alpha particles |(\alpha)| are generally emitted by atoms with a heavy nucleus and will decay to create an atom with a lighter nucleus. Using the A/Z notation, sometimes called the Berzelius’ notation, this type of transformation can be illustrated as follows.

Alpha radiation |(\alpha)| emission creates the following changes:

• The decaying atom loses 2 neutrons and 2 protons.

• Its atomic number |(Z)| decreases by 2.

• Its mass number |(A)| decreases by 4.

• The atom produced by the nuclear reaction is lighter and more stable because there is a more balanced ratio between the number of protons and neutrons.

Negative |\beta| particles can be represented in various ways.

Beta particles |(\beta)| are generally emitted when a light atom contains too many neutrons. The atom’s nucleus decays, transforming a neutron into a proton and emitting a beta particle |(\beta).| 

Based on an early 20th century model, this transformation can be represented using the A/Z notation.

Beta radiation |(\beta)| emission creates the following changes:

• The decaying atom loses 1 neutron and gains 1 proton.

• Its atomic number |(Z)| increases by 1.

• Its mass number |(A)| remains the same.

• The atom produced by this nuclear reaction has essentially the same mass as before, but is more stable due to a more balanced ratio between the number of protons and neutrons.

Gamma radiation |(\gamma)| can be represented in various ways.

Gamma radiation |(\gamma)| often occurs during decay by alpha |(\alpha)| or beta |(\beta)| radiation reactions. It can also be created when a high energy atom loses its energy. The atom is said to change from an excited state to a ground state.

The A/Z notation can be used to explain this emission of energy.

The particles of an atom undergo no change when subjected to this type of gamma radiation |(\gamma):| the number of protons, neutrons and electrons remains the same. Only energy is lost as |\gamma| radiation.