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# Neutron Number Save Print Edit
Neutron Number
• Astrophysics • Atoms and Radioactivity • Electricity • Energy Physics • Engineering Physics • Fields in Physics • Force • Further Mechanics and Thermal Physics • Magnetism • Measurements • Mechanics and Materials • Medical Physics • Nuclear Physics • Particle Model of Matter • Physical Quantities and Units • Physics of Motion • Radiation • Space Physics • Turning Points in Physics • Waves Physics 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.

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. Figure 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. Figure 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:

 Particle Mass in kilograms Electrical charge in coulombs Location neutron 1.67 ⋅ 10 ^ -27 0 Nucleus

### Neutrons and the atom’s 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 atom’s 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 atom’s 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.

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?

The number of neutrons in an atom.

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Where is the neutron number in the nuclide notation?

In the bottom right corner.

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

30.

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Which data do you need to calculate the neutron number?

The atomic number and the mass number.

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What is neutron excess?

Neutron excess exists when there are fewer protons than neutrons.

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What is a neutron?

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

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What is the mass of a neutron?

1.67 x 10^-27 kg.

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What is the charge of a neutron?

0.

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What is the elemental charge of an electron?

-1.

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What is the neutron symbol?

n.

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

99.8%.

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

It is 22,000 times larger.

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

No, it doesn’t.

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

True.

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Where are neutrons located?

In an atom’s nucleus.

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What is another name for neutrons?

Protons and neutrons are also jointly known as nucleons.

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

It makes the atom heavier.

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

Isotope.

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

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

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

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