Unit 6 Notes – Chapters 4 & 12

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 -icacid 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 -ousacid. • HClO: hypochlorous acid • HClO2: chlorous acid

Acid Nomenclature • If the anion in the acid ends in -ate, change the ending to -icacid. • 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 _____

Find the sum of valence electrons of all atoms in the polyatomic ion or molecule. PCl3 Steps to Writing Lewis Structures 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-

Unit 6 Notes – Chapters 4 & 12