Ionic bonding. Not how the ionic radious of the sodium is smaller than its atomic. Also the atoms ioniz to have 8 valence electrons
  Ionic Bonding is when ions of opposite charges(cation and anions) bond together due to these opposite charges and gaining and losing of electrons.
Becoming an ion[]
All atoms have a dream. Like Martin Luther King only it is more self involved. All atoms wish to fill there outer most energy level with 8 electrons(pretty random number but whatevs. its magic). This is why the Noble gases are inert. If you look at the Periodic table all Noble gases have 8 valence electrons or electrons in there outermost energy level(yay there life is completee) This is what causes their very low reactive level. Now Beryllium on the other hand. and pretty much every element in group 1. But anyway lets take Table salt for an example. Table salt of course is an ionic bond(a solt is an ionic bond, Note that there is no Ionic molecule. Molecules refer only to covalent bonding.). Ok so lets take happy happy table salt. The process of ionic bonding begins with two neutral atoms. in this case. Sodium and Chlorine. Now like i told you these two atoms have a life dream of obtaining 8 valence electrons(everyone wants to be noble like neon). This is where we get to the ionization. inorder to create charge one charge must equil more than another. in a neutral atom there are the same number of electrons and protons causing them to equil each other out making a neutral charge. During Ionization the number of protons would not change or else you would change the element(atomic number determines element). so that leaves us with the only subatomic particle with charge leftover the electron( That must make them feel pretty shitty.) The atom either loses or gains electrons depending on the properties. Metals are typically your losers(haha) while Nonmetals would be your resevers or gainers. In a reaction like table salt Chlorine is the nonmetal. chlorine will gain electrons causing the net charge of the electrons to exceed the protons making them negative charged anions. Sodium is a metal and a loser so it will lose electrons causing the number of positive charges to exceed the number of negative charges. bam theres your cation. Hmmm what happens when opposites charges are near each other? o i know i know... They attract forming a bond!!!!! yayayaya we just figured out blues clues. isnt chemistry funnn