 Ionic compounds are composed of electrically charged ions, usually arranged in a neutral crystal lattice. Neutrality is achieved when the positively charged ions (cations) are of exactly the right number to balance the negatively charged ions (anions). Crystals of common salt, for example, comprise as many sodium cations (Na+) as there are chlorine anions (Cl−). Compared to the isolated atoms, the sodium cation has lost an electron and the chlorine anion has gained an electron.