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 -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 Structures1. Find the sum of valence

electrons of all atoms in the polyatomic ion or molecule.

PCl3

5 + 3(7) = 26

Writing Lewis Structures

2. 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

3. Connect the lines to form single bonds. 1 line = 2 electrons

Keep track of the electrons:

Writing Lewis Structures

4. Finish by checking for octets. Hydrogen only needs

2 electrons to be happy

Keep track of the electrons:

Writing Lewis Structures

5. 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-