Unit 6 Notes – Chapters 4 & 12 Mr Nelson 2009

Ionic Compounds – Review Made up of ions Cations (+) & Anions (-) Metals & Nonmetals (or polyatomic ions) Exchange of electrons Charges Balance

Molecular Compounds – Intro No ions Charges will not balance Composed of two nonmetals Sharing of electrons Covalent bonding Naming is based on prefixes

Nomenclature of Binary Compounds If both elements are nonmetals we must use prefixes. The 1st element only gets a prefix if it is greater than 1. 2nd element always gets a prefix and change the ending to -ide

Nomenclature of Binary Compounds Example of a molecular comp: CO2 CO CCl4

Nomenclature of Binary Compounds If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are combined into one. N2O5: dinitrogen pentoxide

Practice PCl5 dihydrogen monoxide SF6 carbon trichloride N2O disulfur hexoxide NO2 nitrogen triiodide

Naming Acids An acid is any compound that starts with a hydrogen When naming an acid: 1st locate the anion (- charge)

Acid Nomenclature If the anion in the acid ends in -ide, change the ending to -ic acid and add the prefix hydro- . HCl: hydrochloric acid HBr: hydrobromic acid

Acid Nomenclature If the anion in the acid ends in -ite, change the ending to -ous acid. HClO: hypochlorous acid HClO2: chlorous acid

Acid Nomenclature If the anion in the acid ends in -ate, change the ending to -ic acid. HClO3: chloric acid HClO4: perchloric acid

Warm Up HBr Chlorous Acid FeS Copper(I) fluoride PBr5 dinitrogen dioxide KSO4 nitrogen monoxide CCl4 hydroiodic acid HNO3 potassium nitrate LiCl phosphoric acid

Lewis Dot Structures ONLY Valence (outer) electrons are involved. You can do Lewis dot structures for atoms and for compounds Lewis dot structures tell you the structure of a molecule of a compound, help predict shape.

Lewis Dot Structure Example Example: Bromine Number of valence electrons _____

Steps to Writing Lewis Structures Find the sum of valence electrons of all atoms in the polyatomic ion or molecule. PCl3 5 + 3(7) = 26

Writing Lewis Structures Arrange element symbols to show how atoms are connected – show electrons as dots. Draw in the valence electrons of each of the atoms Keep track of the electrons:

Writing Lewis Structures Connect the lines to form single bonds. 1 line = 2 electrons Keep track of the electrons:

Writing Lewis Structures Finish by checking for octets. Hydrogen only needs 2 electrons to be happy Keep track of the electrons:

Writing Lewis Structures If the central atom does not have an octet… …form multiple bonds until it does. Example: HCN

Exceptions! Boron and Aluminum are okay with only 6 valence electrons around it BF3

Exceptions If the Lewis Dot Structure you are drawing is an ion: Use [] and specify the charge Add or subtract electrons Positive charges take away electrons Negative charges add electrons Example: Br-