How do you figure out the number of neutrons in a atom?

Expert Answers
pohnpei397 eNotes educator| Certified Educator

Atoms are all made up of three kinds of subatomic particles.  These are electrons, which have negative charges, protons, which have positive charges, and neutrons, which are neutral.  The protons and neutrons make up the nucleus of the atom while the electrons orbit the nucleus.

In order to find the number of neutrons in an atom, take the following steps:

1.  Look up the element on the Periodic Table.

2.  Find the atomic number.

3.  Find the atomic weight.

4.  Round the atomic weight to the nearest whole number.  This tells you the atomic mass.

5.  Subtract the atomic number from the atomic mass.  This gives you the number of neutrons in the atom.

enotechris eNotes educator| Certified Educator

Atoms can have a variable number of neutrons.  That is why the atomic mass is not a whole number; it represents an average weight of all the atoms of an element, which may have different numbers of neutrons. An atom always has the same number of protons, but may have many different numbers of neutrons in the nucleus.  Each of these is known as an isotope of the atom.  So, an atom's proton count always remains the same, but its neutron count may vary.  The second link shows a Periodic Table of Isotopes.  Who knew that hydrogen can have up to 5 neutrons in its nucleus!


atyourservice | Student

atomic mass - atomic number = neutrons

atlaswave | Student

Subtract the atomic mass with atomic number to get the number of neutrons

gutka | Student

no. of neutrons=mass no.-no. of protones

canyousee67 | Student

You must find out the Atomic Number and Atomic mass of an element. Lastly, you subtract the atomis# from the atomic mass.