Everything around us, including ourselves, are made up of atoms. Atoms, in their basic form, consist of a nucleus with one or more positively charged protons - and an equal number of negatively charged electrons spinning around the nucleus. In this form they are electrically uncharged. But when they lose or gain an electron in their outermost shell they become charged, and change important properties. These types of atoms are called ions. In this film you will learn more about ions. You will get to know that atoms always try to achieve noble gas structure, which means a full number of electrons in the outermost electron shell, and that the electrons in the outermost shell are called valence electrons. Finally you will learn that substances on the far left of the periodic table form positive ions because they lose electrons, and substances on the far right of the periodic table form negative ions because they gain electrons.