You will learn: to write and read 4 types of chemical formulas Ionic Compounds Polyatomic Compounds Molecular Covalent Compounds Acids/ Bases

Writing Chemical Formulas When 2 or more elements are chemically combined they are called a molecule or compound. H2 + O2 H2O Na + Cl NaCl atom is the smallest whole unit of an element……. A molecule is the smallest whole unit of a compound……..

**Law of Definite Proportions** Regardless of where or how a pure chemical compound is prepared, it is composed of a fixed proportion of elements. “If it is water it is always 2 hydrogen for every one oxygen… H2O If it is carbon dioxide it is always one carbon for every 2 oxygen…CO2… **Law of Definite Proportions**

Remember: Valence Outer shell electrons involved in chemical reactions Octet Rule: Most stable condition is 8 electrons in outer shell Oxidation #: a + or – number which tells how many electrons were lost gained shared when bonding atoms. Label empty periodic chart

Writing Ionic Binary Compounds (metal + nonmetal) ws 7.1 1. Write + oxidation number atom first 2. Write – oxidation number atom second 3. Do cross-over method for subscripts 4. The compound is in a neutral or “ground state”. The formula’s oxidation #’s must add up to equal zero. 5. Must have lowest common factor Na + N Ca + P Ba + F Mg + O Ba + Sb Li + S Ca + O Sc + Al

Naming Binary Ionic Compounds (Stock System) ws 7.2 1. Write first element name 2. Drop last syllable of second element and add ide 3. Transition metals use Roman Numerals to show oxidation # LiF CuCl NaBr CuCl2 KI FeO WORK SHEET 7.1

Ternary Compounds Polyatomic Ions Poly = many atoms in a group When writing these formulas use the group as a whole. Ca + ClO3 Na + SO4 NH4 + PO4 No need to use ( ) if only one group worksheet 7.3, 7.4

Naming Molcular Compounds 1. Nonmetals only 2. Prefixes give the number of each element ( show numbers) 3. Second element ends in ide 4. O or A at end of prefix is dropped if element begins with a vowel. { monoxide … not---monooxide} {pentoxide … not– pentaoxide} P4S5 tetraphosphorus pentasulfide Si2Br6 disilicon hexabromide CH4 carbon tetrahydride ws-7.7 PUT ON OVERHEAD OF PREFIXES

Writing Formulas for Molecular Covalent Compounds NM + NM Follow wording… do NOT figure oxidation # Antimony tribromide Hexaboron monosilicide Chlorine dioxide ws 7.8

formulas for Molecular Covalent = NM+Nm 1. Make sure Nonmetals + Nonmetals 2. The less electronegative element is written first The element written second will keep its normal negative oxidation #. The first element will keep its normal oxidation # but will be positive. Use the cross-over method The algebraic sum of the ox# must equal zero

Nitrogen + fluorine Oxygen + sulfur Phosphrous + chlorine 1. make sure NM + NM 2. The less electronegative element is written first 3. The element written second will keep its normal negative oxidation #. 4. The first element will keep its normal oxidation # but will be positive. 5. Use the cross-over method 6. The algebraic sum of the ox# must equal zero Nitrogen + fluorine Oxygen + sulfur Phosphrous + chlorine Bromine + carbon

Hydrogen + one other element hydrogen + Polyatomic w/Oxygen Naming Acids 2 common types of Acids Binary Acids Oxyacids Hydrogen + one other element hydrogen + Polyatomic w/Oxygen Hydro + root name & ic Root name + Suffix + acid HBr hydrobromic acid If polyatomic ended in ‘ate’ HCl hydrochloric acid (NO3)- nitrate ion then H2S hydrosulfuric acid HNO3 = nitric acid HCN hydrocyanic acid (SO4)-2 sulfate ion then H2SO4 = sulfuric acid “notice hydrogen not part of name”

Example: HCl----hydrogen chloride is a gas. It is important to remember that these hydrogen – containing compounds are named as acids only when they are in water solutions. Example: HCl----hydrogen chloride is a gas. But dissolved in water it is hydrochloric acid. Memorize: HCl hydrochloric acid HNO3 nitric acid H2SO4 sulfuric acid HC2H3O2 acetic acid H2CO3 carbonic acid H3PO4 phosphoric acid We will learn more acids and bases in chapter 17 later I would put these on an index card

Acids and Bases Hydrochloric Nitric Sulfuric Phosphoric Carbonic Six Acids to memorize Hydrochloric Nitric Sulfuric Phosphoric Carbonic Acetic

Bases: metal + hydroxide Sodium hydroxide Potassium hydroxide Calcium hydroxide

4 ways to name chemicals 1st step----make sure you know which method M+NM NM+NM Ternary Compounds Acids

Nameing Oxyanions