For now we have learned that atoms are basic fundamental building units of all things that are surrounding us. Atoms are made of protons, electrons and neutrons. Protons are positively charged, electrons are negatively charged and neutrons don’t have any charge, so, they are neutral. Together, protons and neutrons are making a nucleus of an atom, the center, core of atom. Around the nucleus, there is electron’s cloud and inside of it, there are electrons. Electrons are circling around the nucleus in their orbitals. Nucleus is by the force holding electrons together. Those electrons that are in the last orbital, the one that is the farthest from the nucleus, they are called ‘valence electrons.’
Because valence electrons are the furthest from the nucleus, here is the weakest effect of the force that is holding them together. Because of this, those electrons from the last orbital (valence electrons) is very easy to ‘kick them out’ from the atom. Electrons on its own, can’t do nothing, so it will search for other atoms or molecules by which it will be attracted. The fact that atom can lose or gain electron, it makes it possible for many chemical connections and bondings.
Atoms that have lost or gained electron, are called ‘ions’ (ion). Atom that have lost electron, becomes a positively charged ion because now it has bigger number of protons than electrons in itself, and lets remember, protons are positively charged while electrons are negatively charged. Positively charged ions are called ‘cations.’
Atom that gains electron, becomes a negatively charged ion, because now it has more electrons than protons in itself, and because of that, it has more of a negative charge. Negatively charged ions are called anions.
Also, atom doesn’t have to have one valence electron. Lets take an atom of oxygen for an example. Oxygen has 8 protons and 8 electrons. From those 8 electrons, 6 are valence.