Physics
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Isotopes

Isotopes

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opes are like different versions of atoms. They can be lighter or heavier than the regular atom because they have different numbers of neutrons and protons. Most isotopes aren't found in nature because they aren't stable, but some of them do exist naturally. There are also some unstable isotopes, like Bismuth-209, that are found in nature because they last a really long time - millions of years or more!

 Left: Helium, a stable isotope. Right: Carbon-14, a known unstable carbon isotope used to date objects
Left: Helium, a stable isotope. Right: Carbon-14, a known unstable carbon isotope used to date objects

Unstable isotopes don't have an equal number of protons and neutrons, which makes them not stable. They don't last long in nature because they eventually break up. When they do, they release energy in the form of radiation. Some unstable isotopes can take millions of years to break up, while others only take seconds. These types of isotopes are usually found in heavy elements.

Scientists call the breaking up process of unstable isotopes "disintegration". You may have heard of this in the news, on TV or in movies. Really heavy atoms like uranium break down into two smaller particles and some leftover energy.

There are lots of examples of unstable isotopes, like Uranium 235, Uranium 238, Plutonium 241, Plutonium 238, Polonium 208, Polonium 209, Cadmium 113, and Cadmium 109.

Some unstable isotopes such as uranium are used to produce energy in nuclear reactors (as illustrated) or for research and medicine

 

Stable isotopes

Stable isotopes are different from unstable ones because they don't break down or decay. These isotopes have either a lack or an excess of neutrons, but they remain stable. You can find many stable isotopes in elements with low atomic numbers.

Copper 63 and Copper 65, Carbon 12 and Carbon 13, Hydrogen 2 and Hydrogen 1, Oxygen 18 and Oxygen 16, Sulphur 34 and Sulphur 32, Iron 56 and Iron 54, and Titanium 47 and Titanium 48 are some examples of stable isotopes.

Isotopes and the nuclide notation

Nuclide notation is a way to determine whether an atom is an isotope. If the atomic number is not equal to the mass number, then it is an isotope.

If the atomic number is less than half of the mass number, the atom has an excess of neutrons. Conversely, if the atomic number is greater than half of the mass number, there is a lack of neutrons.

For example, Carbon 14's nuclide notation is written as 14/6 C. The atomic number of Carbon is 6, so multiplying it by two gives us 12, which we would assume to be the total number of protons and neutrons. However, the nuclide notation tells us there are actually 14 particles in the atom's nucleus. This means that there are eight neutrons (14 particles minus six protons equals eight neutrons), so Carbon 14 an isotope. Moreover, it is also an unstable isotope of carbon.

By using nuclide notation, scientists can determine the number of protons, neutrons, and electrons in an atom. This information is in understanding the atom's behavior and how it interacts with other atoms.

Some classical isotopes names

Some naturally occurring isotopes have been given names. Examples of these include the following isotopes belonging to the hydrogen family:

Protium: 1 proton, 1 electron, and no neutrons. Deuterium: 1 proton, 1 electron, and 1 neutron. Tritium: 1 proton, 1 electron, and 2 neutrons.

 

From left to right: Three well-known isotopes of hydrogen: Protium, Deuterium, and Tritium
From left to right: Three well-known isotopes of hydrogen: Protium, Deuterium, and Tritium

Key Takeaways on Isotopes:

Isotopes are atoms that have different numbers of protons and neutrons.

Isotopes can be either heavier or lighter than the original element.

Isotopes can be either stable or unstable. Stable isotopes and unstable isotopes with a long half-life can be found in nature.

Unstable isotopes undergo a process called disintegration, in which they break up into smaller particles and residual energy.

One can distinguish between an element and its isotopes by comparing its mass number and atomic number.

Isotopes

What is an isotope?

An isotope is an element with a different number of neutrons compared to the basic element.

What is a stable isotope?

A stable isotope is one that does not break up or emit radiation.

What is an unstable isotope?

An unstable isotope is one that has different numbers of neutrons and protons. These isotopes break up, releasing energy and particles in a radiation process. This is also known as radioactive decay.

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