COVALENT COMPOUNDS Unit 2 COVALENT BOND Forms between two non-metals! Electrons are shared! Co= share Valent = electrons Since electrons are shared, no need to balance charges Covalent bonds form molecules. Molecule - group of neutral atoms held together with a covalent bond Diatomic molecules – molecule consisting of 2 atoms MOLECULES H2O2Br2F2I2N2Cl2 Compound composed of molecules is a molecular compound. MOLECULAR COMPOUNDS Molecular Compounds Properties Gases or liquids Low melting/boiling points Usually made from 2 nonmetals bonded covalently Do not conduct electricity (solid or dissolved) Molecular chemical formula shows how many atoms of each element a molecule contains. H2O – Molecular formula of water 2 Hydrogen atoms, 1 Oxygen atom CO2 – Molecular formula for Carbon Dioxide MOLECULAR 1 Carbon atom, 2 Oxygen atoms FORMULAS H:H - Lewis Dot H-H – Structural Formula H2 – Molecular chemical formula LEWIS STRUCTURES COVALENT BONDING To draw a Lewis Structure, one must know the types of atoms in the molecule, the number of atoms in the molecule and the number of valence electrons for each atom in the molecule. DOUBLE & TRIPLE COVALENT BONDS Sharing a pair of electrons creates a single covalent bond Sharing more than one pair of electrons creates double and triple covalent bonds. 2 shared pairs – Double covalent bond 3 shared pairs – Triple covalent bond Carbon, Nitrogen, Oxygen 1. First element is named first, using the full name of the element 2. The second element is named by dropping ending and adding RULES FOR “–ide” NAMING 3. Prefixes are used to denote # COVALENT of each atom present COMPOUNDS 4. Prefix mono- is never used on the first element 5. Do not reduce the subscripts PREFIXES EXAMPLE BF3 boron trifluoride N2O3 dinitrogen trioxide CO2 carbon dioxide CO Carbon monoxide NO H O NAMING 2 PRACTICE N2O5 PROBLEMS CO CCl3 Nitrogen monoxide Dihydrogen monoxide ANSWERS Dinitrogen pentoxide Carbon monoxide Carbon trichloride WRITING PRACTICE PROBLEMS Carbon Nonafluoride Diphosphorous monoxide Tetraoxygen tetrasulfide.