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Writing Formulas and Naming Compounds

WHAT DO ALL THESE THINGS HAVE IN COMMON?

Oxidation and Reduction +1 -1 2Na0 + Cl202NaCl O I L Oxidation is loss of electrons or… xidation s osing Na01e- + Na+1 (Half reaction) Na is oxidized.

R I G 2Na0 + Cl202NaCl Cl0 + 1e-Cl-1 eduction s aining Oxidation and Reduction +1 -1 2Na0 + Cl202NaCl R I G Reduction is gain of electrons or… eduction s aining Cl0 + 1e-Cl-1 (Half reaction) Cl is reduced.

LEO says GER

2Na0 + Cl202Na+1Cl-1 Secret Agent Man Cl Na Oxidizing agent (O.A.) Here’s a little trick Secret Agent Man OIL RIG Oxidizing agent (O.A.) causes a particle to lose e- (by gaining e- itself) Reducing agent (R.A.) causes another particle to gain e- (by losing e- itself) Cl Na Particle Oxidized Particle Reduced R.A. O.A. 2Na0 + Cl202Na+1Cl-1

2Na0 + Cl202Na+1Cl-1 The particle oxidized and the particle reduced are ALWAYS on the same side of the equation! AND the oxidizing agent and reducing agent are ALWAYS on the same side of the equation OIL RIG

So happy togetherrrrrr! Oxidation and reduction always occur together

Ca + S Ca S Practice +2 -2 Ca S S Ca OIL RIG R.A. O.A. +2 -2 OIL RIG Ca + S Ca S R.A. O.A. 1. Assign charges. 2. Particle oxidized ____ 3. Particle reduced ____ 4. Oxidizing agent _____ 5. Reducing agent ____ Then identify: Ca OIL S RIG S O.A. Ca R.A.

Mg + Cl2 Mg Cl2 Practice -1 +2 Mg Cl Cl Mg OIL RIG R.A. O.A. RIG +2 Mg + Cl2 Mg Cl2 R.A. O.A. 1. Assign charges. 2. Particle oxidized ____ 3. Particle reduced ____ 4. Oxidizing agent _____ 5. Reducing agent ____ Then identify: Mg OIL Cl RIG Cl O.A. Mg R.A.

Mg Cl2 -1 +2 Oxidation States Oxidation states Oxidation states indicates how many e- are gained, lost, or shared. Oxidation states Mg Cl2 +2 -1

Rules for Naming Oxidation States 1. In their compounds, the metals of Group 1A always have an oxidation number of +1, the charge on their ions 2. The oxidation number of fluorine (F) is -1 when it is in a compound. +1 -1 NaBr GIVE RULES SHEET AND RULES W.S. HAVE THEM WORK ON RULES W.S. IN CLASS USING RULES AS REFERENCE GO OVER W.S. QUICKLY GO THROUGH RULES; STAR #1, #2, #5, #7 BECAUSE THEY ARE AN ALWAYS. GIVE “OXIDATION STATES” WORKSHEET FOR HOMEWORK…START IN CLASS +1 -1 CuF

Rules for Naming Oxidation States 3. The oxidation number of a monatomic ion is equal to its charge. Fe+3….Oxidation # = +3

Rules for Naming Oxidation States 4. The sum of the oxidation numbers of all the atoms in the formula of a compound is equal to zero. 5. In their compounds, the metals of group 2A always have an oxidation number of +2, the charge on their ions. +1 -2 K2Se +1(2) + -2 = 0 +2 + -2 = 0 K will always be +1 because it is in group 1 +2 -2 CaS +2 + -2 = 0

Rules for Naming Oxidation States 6. In compounds, the oxidation number of oxygen is almost always -2. (Exception: peroxides such as H2O2 or Na2O2 where oxidation number is -1 +1 -1 +1 -1 Na2O2 H2O2 2(+1) + 2(-1) = 0 +2 + -2 = 0 2(+1) + 2(-1) = 0 +2 + -2 = 0

Rules for Naming Oxidation States 7. The oxidation number of an atom of a free element is zero. 8. Hydrogen has an oxidation number of +1 in all compounds, except the metal hydrides, like LiH or CaH2, where oxidation number is -1. Na0 Br20 HF KH +1 -1 Metal hydride

Rules for Naming Oxidation States 9. In combinations involving nonmetals, the oxidation number of the less electronegative element is positive and of the more electronegative element is negative. +2 -3 +4 -2 SO2 Fe3P2 +4 + 2(-2) = 0 +4 + -4 = 0 3(+2) + 2(-3) = 0 +6 + -6 = 0

Polyatomic Ions Some covalently bonded groups of atoms act like single atoms in forming ions. These charged groups of covalently bonded atoms are called radicals or polyatomic ions. SULFITE: SO3-2 AMMONIUM: NH4+1 SULFATE: SO4-2 HYDRONIUM: H3O+1 CHLORITE: ClO2-1 HYDROXIDE: OH-1 CHLORATE: ClO4-1 CYANIDE: CN-1 CHROMATE: CrO4-2 PHOSPHATE: PO4-3

Rules for Naming Oxidation States 10. The algebraic sum of the oxidation numbers of the atoms of a polyatomic ion is equal to its charge. -2 ( ) = the whole ion (S & 3 O’s) have a charge of -2 SO3 -2 SO3 ( ) +4 -2 ___ + -6 = -2 +4

Practice: assign oxidation states (numbers). +2 -2 +1 -1 NaCl MgS Al ZnO H2 CrF2 +2 -2 = 0 +1 -1 = 0 +2 -2 +2 -2 = 0 1-3 on ws +2 -1 +2 + 2(-1) = 0 +2 -2 = 0

Practice: Assign oxidation states (charges). +1 -1 +3 -2 Fe2O3 K2O2 NO2 HBr SrH2 MnBr2 +1 + -1 = 0 +6 + -6 = 0 +2 -1 +1 -1 *Metal hydride *peroxide +2 + -2 = 0 Do 7 +2 + -2 = 0 +2 -1 +4 -2 +2 + -2 = 0 +4 + -4 = 0

Practice: assign oxidation states (numbers). -2 +1 -2 +3 (OH) -1 (Cr2O4)-2 -2 + ___ = -1 +1 ____ + 4 (-2) = -2 ___ + -8 = -2 +6 2(___) + -8 = -2 +3 +2 -2 PRACTICE! (S2O3)-2 ___ + 3 (-2) = -2 ___ + -6 = -2 +4 2(___) + -6 = -2 +2

Practice: assign oxidation states (numbers). +1 +6 -2 ? H2SO4 1(2) + 1x + 4(-2) = 0 2 + 1x + -8 = 0 1x + -6 = 0 Number 4 on sheet 1x = +6 x = +6 +2 +6 + -8 = 0 +8 + -8 = 0

Practice: assign oxidation states (numbers). +1 +7 -2 1(+1) + 1x + 4(-2) = 0 HClO4 K2Cr2O7 1 + 1x -8 = 0 +1 +7 -8 = 0 1x = +7 x = +7 +1 +6 -2 2(+1) + 2x + 7(-2) = 0 PRACTICE! +2 +12 -14 = 0 2 + 2x -14 = 0 2x = +12 x = +6

Al+3 S-2 Al2+3S3-2 = Al2S3 Rb+1 N-3 = Rb3+1N-3 Rb3N1 Refresher Write down elements with their oxidation numbers. *More electronegative is written last. Al+3 S-2 Al2+3S3-2 = Al2S3 2(+3) + 3(-2) +6 -6 = 0 Rb+1 N-3 = Rb3+1N-3 Rb3N1 3(+1) + 1 (-3) +3 -3 = 0

Polyatomic Ions in Compounds Potassium + chlorite Calcium + chromate Magnesium + hydroxide K+1 & (ClO2)-1 = KClO2 +1 -1 = 0 Ca+2 & (CrO4)-2 = CaCrO4 +2 -2 = 0 Mg+2 & (OH)-1 = Mg(OH)2 *Leave polyatomic in parenthesis! +2 + 2(-1) = 0

Writing Chemical Formulas Li and I K and P Rb and C Li and Cr2O7-2 Li+1I-1 LiI K+1P-3 K3P Rb+1C-4 Rb4C PRACTICE Li+1(Cr2O7)-2 Li2Cr2O7

Naming Compounds Is the compound ionic or covalent? If there is a metal or polyatomic ion present, the compound is ionic. If not, it will be classified as covalent.

Naming Ionic Compounds 1. Binary compounds (2 elements) A. Name the positive part B. Follow with the root name of the negative part, ending in –ide (monatomic negative ions end in –ide) CaCl2: Mg3N2: NaF: Calcium Chloride Magnesium Nitride Sodium Fluoride

Naming Ionic Compounds 2. If a metallic ion forms more than one ion (can have more than 1 oxidation #), the name of the ion includes its oxidation number in roman numerals in parentheses after the name of the metallic ion +2 -2 +1 -1 FeO: CuCl: CuCl2: Hg2S: Copper(I)Chloride Iron(II)Oxide +2 -1 -2 +1 Copper(II)Chloride Mercury(I)Sulfide

Naming Ionic Compounds 3. Compounds containing polyatomic ions Name the positive part followed by the name of the negative part LiNO3: Na2SO3: K2SO4: CuNO3: FeSO4 Lithium Nitrate Sodium Sulfite PRACTICE Potassium Sulfate Copper (I) Nitrate Iron (II) Sulfate

Naming Covalent Compounds (2 Nonmetals) 1. Binary compounds end in –ide 2. However, names include prefixes to indicate the number of atoms in the compound (subscript): Di = 2 Tri = 3 Tetra = 4 Penta = 5 Hexa = 6 Hepta = 7 Octa = 8 Nona =9 Deca = 10 *mono is not used for the first element because the 1 is understood.

Let’s try it CO2 SO3 N2O3 N2O Carbon dioxide Sulfur trioxide Dinitrogen trioxide Dinitrogen monoxide

Naming Covalent Compounds 3. Some covalent compounds are known by their common names H2O NH3 H2O2 CH4 CO Water Ammonia Hydrogen peroxide Methane PRACTICE Carbon monoxide

Naming Compounds Ionic Covalent 2 Elements ends in -ide Roman Numeral? (metal & nonmetal) Covalent Nonmetals Nonmetals & H 2 Elements ends in -ide more than 2 elements (*polyatomic ions) ends in –ate or –ite 2 elements ends in -ide Use prefixes: di, Tri, tetra, penta, Hexa, hepta, octa, Nona, deca Ex: CO2 = carbon dioxide P4O10 = tetraphosphorus decoxide Common Names NH3: ammonia H2O: water CH4: methane CO: carbon monoxide Roman Numeral? No Only 1 one oxidation # for the metal Yes More than 1 possible oxidation # for the metal Ex: FeS Fe could be +2 or +3, S is -2 Fe must be +2: Fe+2S-2 = Iron (II) Sulfide