Ar is Argon. Argon is a colorless and odorless gas that is present in a very small part of the atmosphere. The chemical ...

There are 118 elements in the periodic table, each with a unique symbol and atomic number. Symbol: A one or two-letter abbreviation used to represent the element. Atomic number: The number of ...

Atoms of different elements usually have different mass numbers, but they can be the same. For example, the mass number of argon atoms and calcium atoms can both be 40. The symbol for an atom can ...