Chapter 8 Notes Mr Nelson 2010

Chemical Bonds Three basic types of bonds Ionic Covalent Metallic Electrostatic attraction between ions Covalent Sharing of electrons Metallic Metal atoms bonded to several other atoms

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

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 (not PI) change the ending to -ic acid and add the prefix hydro- hydro________ic acid HCl

Acid Nomenclature If the anion in the acid ends in –ate (all PI’s) change the ending to -ic acid. ___________ic acid HClO3

Acid Nomenclature If the anion in the acid ends in –ite (all PI’s) change the ending to -ous acid. _________ous acid HClO2

Acids – Finishing Up If you have the name and need to find the formula Example: Acetic Acid Cross off the –ic and add at –ate Acetate! = C2H3O2- Finish by adding the correct # of H’s (1 for every negative) HC2H3O2 is acetic acid 

Warm Up HBr Chlorous Acid FeS Copper(I) fluoride PBr5 dinitrogen dioxide K2SO4 nitrogen monoxide CCl4 hydroiodic acid HNO3 potassium nitrate LiCl phosphoric acid

Covalent Bonding Covalent bond – atoms share electrons. There are several electrostatic interactions in these bonds: Attractions between electrons and nuclei Repulsions between electrons Repulsions between nuclei

Lewis Dot Structures ONLY Valence (outer) electrons are involved. Lewis dot structures can be drawn for: atoms molecules Lewis dot structures show structure of a molecule, and help predict shape.

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 e- around them 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-