Honors Chemistry Chapter 9 Notes–Chemical Names and Formulas
(studentedition)
Chapter 9 problems: 42, 53, 57, 58, 60, 64, 65, 71, 72, 82-84
good figures in the book to look at.... The figures in this chapter are good to look at – the tables are very important to look at as well.
9.1 Naming Ions
Using Symbols to Write Formulas
Element symbols - element abbreviationex – Arsenic =
Chemical formula - notation that shows the relative # of atoms in a molecule
Formulas use symbols and subscripts ex-
NIB - Kinds of Formulas
The analysis of a compound may tell us that a compound is made of C, H, and O. A analysis may tell us that it is 4 parts C, 10 parts H,1 part O.
formula - a formula that shows the ratio of elements in a compound
ex -
formula - a formula that shows the ratio of elements in a compound
ex -
Note: molecular formula and empirical formula be the same
formula – formula showing the relative numbers of atoms
formula - a formula that shows the way atoms are joined in a molecule
- compounds with the same ratio of atoms, attached in a different order
Examples: butanol vs. diethyl ether – show drawings, condensed formula, structural formulas – going back and forth
Types of Compounds
Ionic - metal and nonmetal or metal and polyatomic ion
metal gives electrons to nonmetal, charges add up to zero, etc...
Covalent (molecular) - 2 nonmetals or metal/metalloid and nonmetal
(depends on electronegativity difference)
9.2Naming and Writing Formulas for Ionic Compounds
positive ions - cationsnegative ions - anionscharges must = 0
rules - if the charges on the ions are the same, “drop ‘em”
- if the charges are different, “criss cross” (apple sauce?)
- if you take, a polyatomic ion, more than once, use parentheses...... fool!
examples:
charges the same -
charges different
polyatomic ions
Naming Ionic Compounds
name front (positive), name back (negative)
binary ionic compounds -
NaClsodium chlorideMgCl2magnesium chloride
Al2O3aluminum oxideNaHsodium hydride
“The big lie” -
ex-CuClCu = +1cuprous chloride
CuCl2Cu = +2cupric chloride
old system (traditional) - low charge = oushigh charge = ic
ex - FeCl2 ferrous chlorideFeCl3 ferric chloride
Latin names to know:
Normal Name / Symbol / Charge / Latin Name / Charge / Latin NameCopper / Cu / +1 / Cuprous / +2 / Cupric
Iron / Fe / +2 / Ferrous / +3 / Ferric
Lead / Pb / +2 / Plumbous / +4 / Plumbic
Tin / Sn / +2 / Stannous / +4 / Stannic
Mercury / Hg / +1 / Mercurous / +2 / Mercuric
new system - Stock System - used for naming compounds with metals that have multiple charges
CuCl isCuCl2 is
ternary compounds - 3 or more elements make up the compound
ex MgCO3
Fe(NO3)3 or
notable exceptions -
room for some more practice:
9.3 Naming and Writing Formulas for Molecular Compounds
First things first: molecular = covalent
Before naming and writing formulas, we’ll learn how to figure out “charges” on atoms as this will help us do this more effectively.
since electrons are shared, there is no definite charge - we assign the more electronegative element the “apparent” negative charge
oxidation # - a number assigned to an atom to show the general distribution of electrons
rules for assigning oxidation #’s
1. Free elements =ex - 2. Oxidation #’s of ions =ex -
3. F = 4. 0 = (usually - peroxides O = )
5. H = (usually - except in metal hydrides) 6. more electronegative atom gets a ( ) charge
7. Ox #’s add up to in compounds 8. Ox #’s = in polyatomic ions
Let’s practice calculating oxidation numbers in general….
examples: FeO, Fe2O3, H2SO4, H2SO3, H2Cr2O7, NO3-1, NO2-1
Now, for application to covalent molecules....
Formula / Oxygen’s Charge / Nitrogen’s Charge / Stock System Name / Traditional NameN2O / -2 / +1
NO / -2 / +2
N2O3 / -2 / +3
NO2 / -2 / +4
N2O5 / -2 / +5
Naming Molecular Compoundsmolecular = covalent
we can use the stock system or prefixes (traditional system) ** prefixes can only be used with covalent compounds
1 = mono2 = di3 = tri4 = tetra5 = penta6 = hexa
don’t use the prefix on the first atom
examples:CO, CO2, PCl3, CBr4, N2O5, SF6
9.4 Naming and Writing Formulas for Acids and Bases
We already know how to name bases (ionic compounds)
acid –a chemical that forms H+ ions in solution
2 types - ( sometimes called )
binary - H and one other type of atom
name them hydro ic acid
examples - HCl, HBr, HF, H2S, H3P
ternary (oxy)-the dog story......
ate - icite - ous
examples - H2SO4, H2SO3, HClO4 through HClO, ...
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