Chapter 19 ¡V Chemical Bonding I. Why do atoms form bonds? 1. Most stable atoms have a filled valence shell. Most of the time this is 8 electrons. 2. Lewis Symbols ¡V electron dot notation showing valence electrons. 3. Atoms form bonds by sharing, gaining, or losing electrons to obtain a filled valence shell. 4. The three major types of chemical bonds are Ionic bonds, Convalent bonds, and Metallic bonds. The type of bond formed depends on the Ionization Energy and electronegativity of the atoms involved. 5. Ionization energy (IE) The energy required to remove a valence electron. Metals have low IE and nonmetals have high IE. 6. Electro-negativity(EN) Very similar to electron affinity. Tendency of an atom to gain electrons, measure of how likely a given atom will steal electrons from another atom. Metals have low EN and nonmetals have high EN. Same reason as electron affinities. II. Ionic bonds. 1. When an atom with low IE is placed next to an atom with a high EN, the second atom may ¡§steal¡ an electron from the first element. 2. This transfer of electrons causes the atom that lost ¡§e¡ to form a smaller cation ( + charged ion) and the atom that gained ¡§e¡ forms a bigger anion ( - charged ion) 3. An ionic bond is the attraction formed between + charged cations and ¡V charged anions. 4. Since metals give e. and nonmetals take, we can say: ionic compounds usually are metals/nonmetals. 5. Example of Li and F using Dot Notation ¡V this e. transfer requires energy. It does take a little energy to remove the e. from the Li, but because both are now stable, the result is a net lowering of energy. B. Size of formed Cations and Anions. 1. Metals tend to get smaller, so they lose e. and thus lose an energy level ¡V cation. 2. Nonmetals tend to gain e. so they are larger ¡V anion. There is no increase in protons, so the nucleus does not pull it in smaller. Instead, it swells to make room. When ionic compounds form, ...