How to find the Number of Protons, Electrons, Neutrons for Argon (Ar)

In this video we’ll use the Periodic table and a few simple rules to find the protons, electrons, and neutrons for the element Argon (Ar). From the Periodic Table we can find the element symbol, atomic number, and atomic mass. Using this information we can find the other information. -----Rules----- Atomic Number = Number of Protons Number of Protons = Number of Electrons (for a neutral element) Mass Number = Number of Protons + Neutrons --------------- Note, when finding protons, neutrons, and electrons for Argon (Ar), remember that Argon is a neutral element (all of the elements on the Periodic Table are listed in their neutral state). That means that the number of protons and electrons will be equal. The Atomic Mass is usually written below the number. If you are confused the Atomic Mass will be the larger number – think of it as more massive than the Atomic Number. Often it also has decimals. If you are not given the Mass Number, it’s best to round to the Atomic Mass to the nearest whole number. For example, with Argon (Ar) we have 39.95. We can round this to 40. Note, that sometimes, for example, you are given a Mass Number of 1 for Hydrogen. This can happen because Hydrogen atoms usually have 0 neutrons. But sometimes a H atom will 1 or 2. These are the three different isotopes for H. They have the same number of protons but different numbers of neutrons and therefore a different Mass Number.

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