Elements are types of atoms that have a unique number of protons.

In fact, from left to right, the periodic table is arranged by the number of protons that each element contains. The periodic table can be used to identify an element in the following three ways.

1. The simplest way to use the periodic table to identify an element is by looking for the element’s name or elemental symbol.
2. The periodic table can be used to identify an element by looking for the element’s atomic number. The atomic number of an element is the number of protons found within the atoms of that element. The key of a periodic table will indicate which number represents the atomic number within each elemental square.
3. The number of protons can be evaluated if the mass number and the number of neutrons of an element are known. The mass number of an element is the number of protons plus the number of neutrons. Therefore, the number of protons can be found by subtracting the number of neutrons from the mass number of the element. Then, the atomic number can be used to identify the element of interest using the periodic table.

Elements can be identified without using a periodic table in the following ways.

• Each element has unique physical properties such as density, melting point, boiling point, etc. These properties can be used to identify an element using a reference book that contains such information about each element.
• Flame tests, atomic spectra, and spectroscopy can be used to identify some elements.