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 ...

After the second level has 8 electrons, the next electron goes into the third level. 3rd Period: Sodium to argon—Electrons go into the third energy level. After the third energy level has 8 electrons, ...

Our bodies require other elements, including non-metal elements such as phosphorus (P), sulphur (S) and chlorine (Cl), and metal elements like potassium (K), sodium (Na), calcium (Ca) and ...