Appliance of science: What happens when you split an atom?

My nine-year-old is obsessed with atoms and that has extended to questions about what happens when you split them, how does it cause an explosion and can atoms be split in space? What are atoms?

Before talking about what happens when you break an atom apart, it would help to understand what an atom is and what they are made of. Atoms are extremely small objects that make up everything around us, they are the basic building blocks for all matter.

Every atom has a nucleus at its centre. The nucleus is made up of two things, neutrons and protons. Neutrons have no charge and protons have positive charges. Together neutrons and protons are called nucleons. These are the main parts we focus on when talking about splitting atoms but atoms also have electrons. Electrons have negative charges and they are not found inside the nucleus, they circle around it.

What happens when you split an atom?

There is a certain amount of energy involved in keeping all the nucleons together in the nucleus. This is called the binding energy. If we put the right strain on the nucleus, the binding energy is not great enough to keep everything together and the nucleus splits.

To split an atom a neutron, travelling at just the right speed, is shot at the nucleus. Under the right conditions the nucleus splits into two pieces and energy is released. This process is called nuclear fission.

The energy released in splitting just one atom is miniscule. However, when the nucleus is split under the right conditions, some stray neutrons are also released and these can then go on to split more atoms, releasing more energy and more neutrons, causing a chain reaction.

This chain reaction very rapidly multiplies the amount of atoms split and the amount of energy released. Under the right conditions a large amount of energy can be released within a fraction of a second resulting in a nuclear explosion.

Can every atom be split like this?

In theory every atom can be split in this way, but in reality size matters. The smaller the nucleus, the more energy required to split the atom. Atoms with larger nuclei can be more successfully split

in this way.

Iron is a very stable element. Atoms with nuclei larger than those of iron are generally considered big enough for nuclear fission in this way. In reality, only a few elements are actually used, Uranium is the most common one used in nuclear reactors.

Splitting in two

When the atom is split it does not split into two exact halves; uranium, for example, has 92 protons in its nucleus. An atom of uranium typically splits into an atom of krypton (36 protons) and an atom of barium (56 protons). This is called binary fission. On rare occasions atoms can be split in three, it is called ternary fission.

What about splitting an atom in space?

NASA has already created a nuclear reactor that can operate in space. This small, compact reactor is said to be able to create enough energy (10 kilowatts of electricity) to power several average households continuously for 10 years.

Although not yet tested in space, this kind of power system has been developed to allow us to travel farther into space, well beyond our current explorations to the Moon.

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