Arranging Elements in the Periodic Table

Look at the periodic table in below:

 The elements are arranged in order of increasing atomic number. The atomic number (number of protons) is located right above the element symbol. Under the element symbol is the atomic mass, or atomic weight. Atomic mass is a weighted average of all naturally occurring .

Notice that two rows of elements  Ce–Lu (commonly called the lanthanides) and Th–Lr (the actinides) — have been pulled out of the main body of the periodic table. If they were included in the main body of the periodic table, the table would be much wider.

Using the periodic table, you can classify the elements in many ways. Two quite useful ways are

✓ Metals, nonmetals, and metalloids

✓ Families and periods