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Radioactivity and types of radiation

In "Nuclear structure and stability" , we discussed that when a nucleus is unstable it can emit particles and energy. This process is called radioactive decay .

Radioactive decay

Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting particles or electromagnetic waves. These emitted particles or electromagnetic waves are called radiation .

When a nucleus undergoes radioactive decay, it emits radiation and the nucleus is said to be radioactive. We are exposed to small amounts of radiation all the time. Even the rocks around us emit radiation! However some elements are far more radioactive than others. Even within a single element, there may be some isotopes that are more radioactive than others simply because they contain a larger number of neutrons. These radioactive isotopes are called radioisotopes .

Radiation can be emitted in different forms. There are three main types of radiation: alpha, beta and gamma radiation. These are shown in [link] , and are described below.

Types of radiation

Alpha ( α ) particles and alpha decay

An alpha particle is made up of two protons and two neutrons bound together. This type of radiation has a positive charge . An alpha particle is sometimes represented using the chemical symbol H e 2 + , because it has the same structure as a Helium atom (two neutrons and two protons) ,but without the two electrons to balance the positive charge of the protons, hence the overall charge of +2. Alpha particles have a relatively low penetration power. Penetration power describes how easily the particles can pass through another material. Because alpha particles have a low penetration power, it means that even something as thin as a piece of paper, or the outside layer of the human skin, will absorb these particles so that they can't penetrate any further.

Alpha decay occurs in nuclei that contain too many protons, which results in strong repulsion forces between these positively charged particles. As a result of these repulsive forces, the nucleus emits an α particle. This can be seen in the decay of Americium (Am) to Neptunium (Np).


95 241 Am 93 237 Np + α particle

Let's take a closer look at what has happened during this reaction. Americium (Z = 95; A = 241) undergoes α decay and releases one alpha particle (i.e. 2 protons and 2 neutrons). The atom now has only 93 protons (Z = 93). On the periodic table, the element which has 93 protons (Z = 93) is called Neptunium. Therefore, the Americium atom has become a Neptunium atom. The atomic mass of the neptunium atom is 237 (A = 237) because 4 nucleons (2 protons and 2 neutrons) were emitted from the atom of Americium.

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Beta ( β ) particles and beta decay

In nuclear physics, β decay is a type of radioactive decay in which a β particle (an electron or a positron) is emitted. In the case of electron emission, it is referred to as beta minus ( β -), while in the case of a positron emission as beta plus ( β +).

An electron and positron have identical physical characteristics except for opposite charge.

Questions & Answers

How do hydrogen and chlorine atoms bond covalently in a molecule of hydrogen chloride?
Tiny Reply
what is the parallel circuit
Philani Reply
how many moles of H2O can be formed if 12,5 moi CH4 reacts with sufficient NH3 and O2
Nomcebo Reply
what atoms form covalent bond
hehe Reply
The combination of two non metals
combined two non-metals 😊
what is a mole
Thandeka Reply
a mole is a measure of large quantities of small entities such as atoms, molecules etc
what does STP stand for?
STP stands for Standard Temperature and Pressure.
A car drives straight off the edge of a cliff that is 54m high. The police at the scene of the accident observed that the point of the impact is 130m from the base of the clif. Calculate the initial velocity of the car when it went ovet the clif.
hanyani Reply
wat happens to current if resistors are in parallel connection
Mosima Reply
more current flows from the source that would flow for any of them individually,so the total total resistance is lower
In the parallel circuit the current is divided among the resistors
what are the isotopes
Tlotlisang Reply
are different types of the same elemant but with different mass or atomic no.
i sotopes are different type of element with same atomic number but different mass number
yes i forgot some details😁
next quetion plz
why don't we insert the negative sign for 5 × 10 - 9 when substituting
Mpho Reply
Why does an enclosed gas exert pressure on the walls of a container
Palesa Reply
State the gay lussacs law
Anna Reply
what is the coefficient of Na in order to balanced the equation?_Na + MgCl2=2NaCl+Mg?
Arcel Reply
the combining power of an element, especially as measured by the number of hydrogen atoms it can displace or combine with.
Dealon Reply
download periodic table from play Store...it will explain everything to u
what are orbitals
Sphe Reply
examples of atoms whose Valence energy levels are not full and more to bond and become more stable
What is a valency
What a lone pairs...
Valency is the number of electrons than an atom must gain, lose or share to achieve noble gas configuration.
what is vacuum
Njabulo Reply
Vacuum, space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. It is a condition well below normal atmospheric pressure and is measured in units of pressure (the pascal).

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Source:  OpenStax, Siyavula textbooks: grade 11 physical science. OpenStax CNX. Jul 29, 2011 Download for free at http://cnx.org/content/col11241/1.2
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