QUESTION #109

# What are the number of neutrons in each of elements? (Not isotopes of elements).

All elements, except the most common form of hydrogen, contain neutrons to help hold the positively charged protons in their nucleus together. Neutrons add to the strong nuclear force without adding to the mutually repulsive electrical force of the protons.

Every element can exist in different forms, called isotopes. Each isotope of an element contains the same number of protons but different numbers of neutrons. While some isotopes are stable and others are not, they are ALL called isotopes just as all siblings in a family are brothers or sisters. Even though there is usually a more abundant form of each element's nucleus, there is no one 'main' nucleus with a 'non-isotope' designation as your question implies.

If you look at the isotopes of different elements, the general rule is that the number of neutrons is similar to the number of protons in nuclei at the beginning of the periodic table (low number of protons). Carbon, for example, has a stable nucleus when its 6 protons are joined by 6 neutrons. When you get to elements with a larger number of protons in their nucleus, the ratio of neutrons to protons increases. Uranium, for example, has the largest naturally occurring nucleus with 92 protons and over 140 neutrons.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

You can figure out the most common configuration of elements by looking at the periodic table of elements. There, elements are arranged according to their atomic number - the number of protons in the nuclei. The notation is as follows:

AZX

where, A is the mass number of the element's nuclei, and Z is the atomic number (X stands for the element symbol, for example: H is for hydrogen, O is for oxygen, Na for sodium, etc.) The mass number gives you the total number of protons and neutrons in the nucleus of that element. Therefore, the number of neutrons is given by A-Z.