This bond gives the molecule completely different chemical properties than its parent elements. We can mix it with food or water with little consequence. Yet sodium is a metal that is violently reactive with water. If sodium comes into contact with water, the hydrogen gas that is released will actually burst into flames. And chlorine is a highly toxic, greenish-colored gas.
Chlorine is so toxic that it was used during World War II as a poison gas.
We can represent the actual number of electrons in an atom's valence shell by drawing each valence electron as a dot surrounding the element symbol. Ionic Bonding Let's look at an example. We know that the capacity of the 3rd shell is 8, so chlorine will try to pick up another electron to fill its outermost shell. For some atoms it is easier to lose electrons than to pick up new ones. Thus chlorine and sodium are a perfect match for each other.