Identifying Bonds (Ionic vs. Covalent) Double & Triple Covalent Bonds

How can you tell if a bond is IONIC or COVALENT? Nonmetals & Metals = ionic bond All Nonmetals = covalent bond

Writing Covalent Formulas Place the nonmetal furthest to the left on the periodic table first. If both elements are in the same group/family then place the element closest to the top first. Examples: Cl + H = HCl O + 2H = H2O 4Cl + C = CCl4

Steps for Building a Dot Structure Ammonia, NH3 1. Decide on the central atom; never H. Therefore, N is central on this one 2. Add up the number of valence electrons that can be used. H = 1 and N = 5 Total = (3 x 1) + 5 = 8 electrons / 4 pairs

Building a Dot Structure 3. Form a single bond between the central atom and each surrounding atom (each bond takes 2 electrons!) H N 4. Remaining electrons form LONE PAIRS to complete the octet as needed (or duet in the case of H). H •• N 3 BOND PAIRS and 1 LONE PAIR.

Building a Dot Structure H •• N Check to make sure there are 8 electrons around each atom except H. H should only have 2 electrons. This includes SHARED pairs. 6. If you have more electrons in the drawing than in step 2, you must make double or triple bonds. If you have less electrons in the drawing than in step 2, you made a mistake!

Carbon Dioxide, CO2 1. Central atom = 2. Valence electrons = 3. Form bonds. C 4 e- O 6 e- X 2 = 12 e- Total: 16 valence electrons This leaves 12 electrons (6 pair). 4. Place lone pairs on outer atoms. 5. Check to see that all atoms have 8 electrons around it except for H, which can have 2.

Carbon Dioxide, CO2 C 4 e- O 6 e- X 2 = 12 e- Total: 16 valence electrons How many are in the drawing? 6. There are too many electrons in our drawing. We must form DOUBLE BONDS between C and O. Instead of sharing only 1 pair, a double bond shares 2 pairs. So one pair is taken away from each atom and replaced with another bond.

Lewis-dot Structure: NaCl 04/10/99 Na → 1 valence e- Cl → 7 valence e- s Total = 8 e- s Na Cl 9

Lewis-dot Structure: NaCl 04/10/99 Na → 1 valence e- Cl → 7 valence e- s Total = 8 e- s Na Cl 10

Lewis-dot Structure: NaCl 04/10/99 Na → 1 valence e- Cl → 7 valence e- s Total = 8 e- s X Na Cl It must be an Ionic Bond! 11

Ionic bonding: NaCl 04/10/99 Cl Cl – Na+ Na

Ionic bonding: Li2O 04/10/99 Li Li + O O 2–

Carbon Monoxide, CO 1. Valence electrons = 2. Form bonds. C 4 e- O 6 e- Total: 10 valence electrons

Nitrous Oxide, N2O 1. Valence electrons = 2. Form bonds. N 5 e- X 2 = 10 e- O 6 e- Total: 16 valence electrons