1. Covalent Molecules Quiz on Friday, January 10

2. Review of Ionic Bonding Ionic bonds occur between a metal and a nonmetal, or between a positively charged particle and a negatively charged particle. Ionic bonds occur between a metal and a nonmetal, or between a positively charged particle and a negatively charged particle. Ionic bonds involve a transfer of electrons. Ionic bonds involve a transfer of electrons. Can you identify which of the following are joined by ionic bonds? Can you identify which of the following are joined by ionic bonds? –NaCl- K 3 N - MgBr 2 –CO 2 - N 2 - Al 2 O 3

3. Covalent Bonding Covalent bonds occur between two nonmetals. Covalent bonds occur between two nonmetals. A molecule is formed when two or more atoms bond covalently. A molecule is formed when two or more atoms bond covalently. Covalent bonds involve sharing of electrons. Covalent bonds involve sharing of electrons.

4. Diatomic Molecules Certain elements occur in nature as diatomic molecules and not as single atoms (more stable as the molecule) Certain elements occur in nature as diatomic molecules and not as single atoms (more stable as the molecule) Examples: Examples: –H 2, N 2, O 2, –F 2, Cl 2, Br 2, I 2 Diatomic Molecules Diatomic Molecules are bonded together are bonded together by covalent bonds. by covalent bonds.

5. Lewis Structures Use electron-dot diagrams to show how electrons are arranged in molecules. Use electron-dot diagrams to show how electrons are arranged in molecules. A dot represents a valence electron and a line represents a shared pair of valence electrons. A dot represents a valence electron and a line represents a shared pair of valence electrons. HH++O=O H H or O H H C = ++ClC + + C or Cl H2OH2O CCl 4

6. Important Definitions Chemical Formula: a representation, using symbols, showing the different types and number of atoms that make up a given compound or molecule Chemical Formula: a representation, using symbols, showing the different types and number of atoms that make up a given compound or molecule Subscript: small number, written behind an element, showing how many atoms of that element are found in a compound or molecule Subscript: small number, written behind an element, showing how many atoms of that element are found in a compound or molecule

7. Naming Molecular Compounds The first element written in the formula is always written first, using the element name. The first element written in the formula is always written first, using the element name. The second element is named using the root of the element and the suffix “-ide”. The second element is named using the root of the element and the suffix “-ide”. Prefixes are used to indicate the number of atoms of each type that are present in the compound. Prefixes are used to indicate the number of atoms of each type that are present in the compound. –Exception: Do not use the prefix mono- for the first element Drop the final letter of the prefix when the element name begins with a vowel Drop the final letter of the prefix when the element name begins with a vowel

8. Table 1: Common Prefixes Used in Covalent Compounds Number of atoms Prefix Prefix 1Mono-6Hexa- 2Di-7Hepta- 3Tri-8Octa- 4Tetra-9Nona- 5Penta-10Deca-

9. What Does Naming Look Like? 1. CCl 4 : 2. CO: 3. NF 3 : 4. NO: Carbon tetrachloride Carbon monoxide Nitrogen trifluoride Nitrogen monoxide

10. Now, you practice 1. CO 2 : ________________________________ 2. SO 2 : ________________________________ 3. S 2 O 3 : _______________________________ 4. N 2 O: _______________________________ 5. PCl 5 : ________________________________ 6. OF 2 : _____________________________ 7. N 2 O 4 : _____________________________ 8. S 4 N 4 : ______________________________ 9. SiCl 4 : ______________________________ 10. BF 3 : ________________________________ Oxygen difluoride Sulfur dioxide Disulfur trioxide Dinitrogen monoxide Phosphorous tetrachloride Carbon monoxide Dinitrogen tetroxide Tetrasulfur tetranitride Silicon tetrachloride Boron trifluoride

11. What’s the formula? 1. Selenium hexafluoride: ___________ 2. Disilicon hexabromide: __________ 3. Diboron silicide: __________ 4. Iodine pentafluoride: ________ 5. Hexaboron silicide: ________ 6. Diboron tetrabromide: _______ 7. Diphosphorous pentoxide: ______ 8. Carbon tetrafluoride: ________ 9. Tetraphosphorous pentasulfide: _______ 10. Hexasulfur oxide: _________ IF 5 Si 2 Br 6 SeF 6 CF 4 B 2 Si B 6 Si B 2 Br 4 P2O5P2O5 P4S5P4S5 S6OS6O