How to Find the Number of Neutrons in an Atom

Determining the number of neutrons in an atom is quite simple, you don’t even need to do any experiments. To calculate the number of neutrons in a normal atom or in an isotope, simply prepare a periodic table and follow these instructions.

Table of Contents

Find the number of neutrons in an ordinary atom

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/0/05/Find-the-Number-of-Neutrons-in-an-Atom-Step-1-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-1-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ 0/05/Find-the-Number-of-Neutrons-in-an-Atom-Step-1-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-1-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Locate the element on the periodic table. For example, we will find the element osmium (Os) in the sixth row from the top.

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/f/f0/Find-the-Number-of-Neutrons-in-an-Atom-Step-2-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-2-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ f/f0/Find-the-Number-of-Neutrons-in-an-Atom-Step-2-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-2-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Find the atomic number of the element. This is the most visible number that follows each prime and is above that prime symbol (there are no other numbers on the table we’re using). The atomic number is the number of protons in a single atom of that element . Os is the number 76, meaning that in an osmium atom there are 76 protons.

The number of protons never changes in the element; it is basically the identifying characteristic of an element.

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/0/0b/Find-the-Number-of-Neutrons-in-an-Atom-Step-3-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-3-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ 0/0b/Find-the-Number-of-Neutrons-in-an-Atom-Step-3-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-3-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Find the atomic weight of the element. This number is usually found below the prime symbol. Note, the periodic table in this example only has the atomic number, not the atomic weight. Not all periodic tables are like that. Osmium has an atomic weight of 190.23.

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/4/49/Find-the-Number-of-Neutrons-in-an-Atom-Step-4-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-4-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ 4/49/Find-the-Number-of-Neutrons-in-an-Atom-Step-4-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-4-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Round the atomic weight to the nearest whole number to get the atomic mass. For example, 190.23 would be rounded to 190, so the atomic mass of osmium is 190.

Atomic weight is the average value of isotopes of the same chemical element, which is why it is not usually an integer.

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/f/f0/Find-the-Number-of-Neutrons-in-an-Atom-Step-5-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-5-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ f/f0/Find-the-Number-of-Neutrons-in-an-Atom-Step-5-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-5-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Subtract the atomic number from the atomic mass. Since most of the atomic mass is the mass of protons and neutrons, subtracting the number of protons from the atomic mass (i.e. atomic number) gives you the number of neutrons in an atom. The number after the decimal point represents the very small mass of the electrons in the atom. In this example, we have: 190 (atomic mass) – 76 (protons) = 114 (neutrons).

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/4/43/Find-the-Number-of-Neutrons-in-an-Atom-Step-6-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-6-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ 4/43/Find-the-Number-of-Neutrons-in-an-Atom-Step-6-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-6-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Memorize the formula. To find the number of neutrons, we just need to apply the following formula:

N = M – n
- N = number of neutrons
- M = atomic mass
- n = atomic number

Find the number of neutrons in the isotope

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/a/a3/Find-the-Number-of-Neutrons-in-an-Atom-Step-7-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-7-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ a/a3/Find-the-Number-of-Neutrons-in-an-Atom-Step-7-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-7-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Locate the element on the periodic table. We take the element isotope carbon-14 as an example. Since the isotope form of carbon-14 is simply carbon (C), look for carbon on the periodic table (second row from the top).

READ More: How to Go on an Adventure

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/5/51/Find-the-Number-of-Neutrons-in-an-Atom-Step-8-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-8-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ 5/51/Find-the-Number-of-Neutrons-in-an-Atom-Step-8-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-8-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Find the atomic number of the element. This is the most visible number that follows each prime and is above that prime symbol (there are no other numbers on the table we’re using). The atomic number is the number of protons in a single atom of that element . C is the number 6, which means that in one carbon atom there are 6 protons.

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/a/ad/Find-the-Number-of-Neutrons-in-an-Atom-Step-9-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-9-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ a/ad/Find-the-Number-of-Neutrons-in-an-Atom-Step-9-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-9-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Find the atomic mass. This is extremely easy with isotopes because they are named after their atomic mass. For example, carbon-14 would have an atomic mass of 14. Once you have found the atomic mass of the isotope, the remaining steps to find the number of neutrons will be the same as for a normal atom.

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/1/18/Find-the-Number-of-Neutrons-in-an-Atom-Step-10-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-10-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ 1/18/Find-the-Number-of-Neutrons-in-an-Atom-Step-10-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-10-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Subtract the atomic number from the atomic mass. Since most of the atomic mass is the mass of protons and neutrons, subtracting the number of protons from the atomic mass (i.e. atomic number) gives you the number of neutrons in an atom. The number after the decimal point represents the very small mass of the electrons in the atom. In this example, we have: 14 (atomic mass) – 6 (protons) = 8 (neutrons).

{“smallUrl”:”https://www.wikihow.com/images_en/thumb/c/c2/Find-the-Number-of-Neutrons-in-an-Atom-Step-11-Version-2.jpg/ v4-460px-Find-the-Number-of-Neutrons-in-an-Atom-Step-11-Version-2.jpg”,”bigUrl”:”https://www.wikihow.com/images/thumb/ c/c2/Find-the-Number-of-Neutrons-in-an-Atom-Step-11-Version-2.jpg/v4-728px-Find-the-Number-of-Neutrons-in-an-Atom- Step-11-Version-2.jpg”,”smallWidth”:460,”smallHeight”:345,”bigWidth”:728,”bigHeight”:546,”licensing”:”<div class=”mw-parser-output “></div>”}

Memorize the formula. To find the number of neutrons, we apply the following formula:

N = M – n
- N = number of neutrons
- M = atomic mass
- n = atomic number

Advice

The mass of an element is largely the mass of protons and neutrons, while the masses of electrons and other elements are negligible (near zero). Since the mass of a proton is approximately equal to the mass of a neutron, and the atomic number represents the number of protons, we simply subtract the number of protons from the total mass.
If you don’t remember what the numbers on the periodic table mean, remember that the periodic table is usually built on the atomic number (i.e. the number of protons), starting at 1 (hydrogen) and increasing by one unit from left to right, ending in 118 (ununoctium). Since the number of protons is the defining characteristic of each atom, it is the simplest feature against which to arrange the elements. (For example, an atom with 2 protons is always helium, just as an atom with 79 protons is always gold.)

Steps

Find the number of neutrons in an ordinary atom

Find the number of neutrons in the isotope

Advice

Related Posts