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Neutron Number

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Neutron Number

The neutron number refers to the total number of neutrons in the nucleus. If the number of neutrons is larger than the number of protons, the atom has a neutron excess.

Reading the neutron number

To identify the neutron number, you need to read the elements nuclide notation. The neutron number is located in the lower right corner of the nuclide notation, as in this example of Iron 56:

However, the neutron number is not always specified and thus may need to be calculated.

Neutron Numbers. Atom model of tritium. StudySmarterFigure 1. Tritium, which is an isotope of hydrogen. Its nuclide notation indicates that there are three particles in the nucleus: one proton and two neutrons. Source: Manuel R. Camacho, StudySmarter.

Calculating the neutron number

To calculate the neutron number, use the nuclide notation as shown below:

In the case of Iron 56, this looks as follows:

Neutron excess

The nuclide notation defines the number of particles in the nucleus in the upper-left corner, while the number of protons is given in the lower-left corner, as in this example of Iron 56:

Iron has 26 protons, as indicated by the atomic number in the lower-left corner, and a total of 56 particles in the nucleus, as shown in the upper-left corner. You might expect the number of protons and other particles in the nucleus to be equal, but that is not the case. Multiplying 26 by two would give you 52, whereas the atomic number 56 indicates that there are four additional particles in the atoms nucleus. There is, therefore, a neutron excess of four.

Neutrons and isotopes

An atom with either a lack or an excess of neutrons is called an isotope. Some isotopes break up after some time, which produces radiation in the form of particles such as photons, beta particles and others. There can be many isotopes for a single atomic element.

Neutron Numbers. Isotopes. Hydrogen. StudySmarterFigure 2. Hydrogen isotopes with different numbers of neutrons in the nucleus. From left to right: no neutron, one neutron, and two neutrons. Source Manuel R. Camacho, StudySmarter.

What is a neutron?

A neutron is a particle located in the centre of an atom alongside protons. Both neutrons and protons are also known as nucleons. Neutrons have a neutral charge and are one of two types of particles that contribute a greater amount of mass to an atom. The characteristics of neutrons are shown below:

ParticleMass in kilogramsElectrical charge in coulombsLocation
neutron1.67 ⋅ 10 ^ -270Nucleus

Neutrons and the atoms mass

Neutrons are one of two types of particles that make up most of an atoms mass. The more neutrons an atom has, the heavier it is. Neutrons have a mass that is 1836.15 times larger than that of an electron and are just a bit heavier than protons.

Neutrons and the atoms charge

Neutrons have a neutral electrical charge. Because of this, when an atom has a neutron excess, it does not change its electrical nature.

Neutrons and the atoms relative charge

When thinking about atomic charges, it helps to work with the concept of relative charge. The relative electrical charge of a neutron is 0. A neutrons relative charge is indicated as below:

Neutron Numbers - Key takeaways

  • The neutron number indicates how many neutrons there are in total in an element's atom.
  • The difference between the neutron number and the atomic number indicates the neutron excess.
  • Neutrons are one of two particles that add a significant amount of mass to an atom.
  • Neutrons are almost 1836.15 times heavier than electrons.
  • Neutrons and protons have similar masses.
  • Neutrons have a neutral charge and only add mass to an atom.

Frequently Asked Questions about Neutron Number

To determine the number of neutrons, you need to read the nuclide notation and apply the following formula:


Neutron number = Mass number-Atomic number.

The neutron number indicates the number of neutrons in an atom.

Neutron excess indicates that there are more neutrons than protons in the atom’s nucleus. It is determined by subtracting the number of protons from the number of neutrons.

Final Neutron Number Quiz

Question

What is the neutron number?

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Answer

The number of neutrons in an atom.

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Question

Where is the neutron number in the nuclide notation?

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Answer

In the bottom right corner.

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Question

What is the neutron number in this element: Fe 56?

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Answer

30.

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Question

Which data do you need to calculate the neutron number?

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Answer

The atomic number and the mass number.

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Question

What is neutron excess?

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Answer

Neutron excess exists when there are fewer protons than neutrons.

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Question

What is a neutron?

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Answer

An atomic particle that is located in the atom’s nucleus.

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Question

What is the mass of a neutron?

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Answer

1.67 x 10^-27 kg.

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Question

What is the charge of a neutron?

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Answer

0.

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Question

What is the elemental charge of an electron?

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Answer

-1.

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Question

What is the neutron symbol?

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Answer

n.

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Question

In percentage, how similar are the masses of neutrons and protons?

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Answer

99.8%.

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Question

How large is the mass of a neutron compared to that of an electron?

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Answer

It is 22,000 times larger.

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Question

If the atom has an excess of charge, does that change its electrical charge?

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Answer

No, it doesn’t.

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Question

Neutrons are particles that contribute mass to the atom. True or False?

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Answer

True.

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Question

Where are neutrons located?

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Answer

In an atom’s nucleus.

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Question

What is another name for neutrons?

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Answer

Protons and neutrons are also jointly known as nucleons.

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Question

What is the effect of there being more neutrons in an atom?

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Answer

It makes the atom heavier.

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Question

What is the name of an atomic element with an excess of neutrons?

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Answer

Isotope.

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Question

What can happen when an atom has more neutrons than protons?

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Answer

The atom can break into smaller particles such as electrons, alpha particles, and elements of lower atomic mass.

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Question

What happens when, due to an excess of neutrons, the atom breaks into smaller particles?

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Answer

It produces radiation.

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