MOLECULAR COMPOUNDS What are they and how to name them? Definition: A compound formed when atoms of two or more different elements share electrons Usually formed between 2 or more non-metals and are also called covalent compounds Molecular Compounds Smaller compounds with 2-3 atoms linked Lattice structure (solids) What do they form? Non-metal to non-metal Metal to non- metal What bonds with what? Atoms share electrons to complete valence shells Transfer of electron opposite charges attract How atoms bond? Molecular Compounds Ionic Compounds Ionic vs. Molecular? Ionic Covalent Naming Molecular Compounds Naming molecular compounds is different from ionic and polyatomic compounds. In molecular compounds the name uses a prefix to indicate the number of each atom present. Example: Carbon Dioxide tells us it is made of carbon and oxygen in a ratio of 1 carbon atoms to 2 oxygen atoms. Prefixes (P 4 O 10 ) tetraphosphorous deca oxide 10deca 9nona 8octa 7hepta (SF 6 ) sulfur hexa fluoride 6hexa (PBr 5 ) phosphorus penta bromide 5penta (CF 4 ) carbon tetra fluoride 4tetra (SO 3 ) sulfur tri oxide 3tri (CO 2 ) carbon di oxide 2di (CO) carbon mono xide 1mono ExampleNumber of atoms Prefix Writing Names 1.Count the # of atoms of the first element. 2.Write the prefix for this number followed by the name of the first element. If there is only one of the first element we leave out the prefix. 3.Count the # of atoms of the second element. 4.Write the prefix for this number followed by the name of the element using the suffix ide. Examples N2O4N2O4 Nitrogen atoms = 2 dinitrogen Oxygen atoms = 4 tetraoxide Full name = dinitrogen tetraoxide C2F6C2F6 Carbon atoms = 2 dicarbon Fluoride atoms = 6 hexafluoride Full name = dicarbon hexafluoride Writing Formulas 1.Write the symbol for the elements. 2.Write the subscript for the number of atoms represented by the prefix. 3.Noticethe ratio in the formula is not reduced to its simplest form like ionic compounds. sulfur trioxide SO 3 diphosphorus pentasulfide P2S5P2S5 Examples Diatomic Elements Some elements are diatomic. This means they exist naturally as two of the same element bonded together Examples: Hydrogen gasH 2 Bromine liquidBr 2 Oxygen gasO 2 Iodine solidI 2 Nitrogen gasN 2 Fluorine gasF 2 Chlorine gasCl 2