The Periodic Table is a well-organized chart that contains all 118 known elements in the universe. These elements are the ...

The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic ...

The same chemical symbols are used all over the world ... is a substance that contains atoms of two or more different elements, chemically joined together. For example, water is a compound ...

The formula H₂O shows that water is made from two atoms of hydrogen (H) bonded to one atom of oxygen (O). Katie: Time for some science. And today it's a chemistry classic, the periodic table.