The number of protons in an atom also determines the chemical behavior of the element. These symbols are used internationally. Typically, a symbol is the truncated name of the element or the truncated Latin name of the element. Click here for a list of the elements and their symbols. Though individual atoms always have an integer number of amus, the atomic mass on the periodic table is stated as a decimal number because it is an average of the various isotopes of an element.
Isotopes can have a weight either more or less than the average.
The electron configuration is the orbital description of the locations of the electrons in an unexcited atom. Using principles of physics, chemists can predict how atoms will react based upon the electron configuration. They can predict properties such as stability, boiling point, and conductivity. Typically, only the outermost electron shells matter in chemistry, so we truncate the inner electron shell notation by replacing the long-hand orbital description with the symbol for a noble gas in brackets. This method of notation vastly simplifies the description for large molecules.