unit 6 notes – chapters 4 & 12 mr nelson 2009. ionic compounds – review made up of ions...
TRANSCRIPT
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-