Molecular Compounds & Acids Naming Molecular Compounds & Acids

Molecules Molecule – two or more atoms covalently bound together Diatomic element – two of the same atom bound together

Diatomic Molecules The Magnificent 7 These atoms never exist alone. Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, and Iodine These atoms never exist alone. When in the elemental form, they occur as a pair For example: Br  Br2 I  I2 N  N2 Cl  Cl2 H  H2 O  O2 F  F2

Binary Molecular Compounds Binary covalent compounds contain 2 nonmetals Before you can name binary covalent compounds, you MUST know the prefixes! Mono Di Tri Tetra Penta Hexa Hepta Octa Nona Deca 1 2 3 4 5 6 7 8 9 10

Rules for naming Binary Covalent Compounds Name the prefix for the number of atoms of the first element Then name the first element Name the prefix for the number of atoms of the second element Than name second element with the ending -ide

Note… If the 1st prefix is mono….DROP IT! Example: CO = carbon monoxide NOT monocarbon monoxide When the prefix ends in an o or a, and the name of the element begins with an o or a, one o or a is often dropped CO = carbon monoxide NOT carbon monooxide

Examples What is the name of N2O4? N2  di nitrogen O4  tetra oxide Since oxide begins with a vowel, we will drop the a in tetra Dinitrogen tetroxide

More examples Name SO2 S  mono sulfur But mono is with the 1st element, so it will be dropped  sulfur O2  dioxide Sulfur dioxide

More examples Write the formula for dichlorine monoxide Dichlorine  Cl2 Monoxide  O Cl2O

More examples Write the formula for disulfur dichloride Disulfur  S2 Dichloride  Cl2 S2Cl2

Rules for Writing Formulas Two sets of rules, ionic and covalent To decide which to use, decide what the first word is. If is a metal or polyatomic ion use ionic. If it is a non-metal use covalent.

Hydrates Some compounds trap water crystals when they form. These are hydrates. Both the name and the formula needs to indicate how many water molecules are trapped. In the name we add the word hydrate with a prefix that tells us how many water molecules.

Hydrates In the formula you put a dot and then write the number of molecules. Calcium chloride dihydrate = CaCl2·2H2O Chromium (III) nitrate hexahydrate = Cr(NO3)3· 6H2O

Acids Acids can be recognized because the start with H Acids are in aqueous solution (aq) Examples HCl (aq) H2SO4 (aq) HI (aq)

Rule #1 - naming acids If the anion ends in –ide, the acid will be named… Hydro (root) – ic acid Examples: HCl = Hydrochloric acid HI = Hydroiodic acid H2S = Hydrosulfuric acid

Rule #2 – naming acids If you have an H plus an anion ending in –ate, the acid will be named… (root) – ic acid Examples H2SO4 (sulfate) = Sulfuric acid HNO3 (nitrate) = Nitric acid H3PO4 (phosphate) = Phosphoric acid

Rule # 3 – naming acids If you have an H plus an anion ending in –ite, the acid will be named… (root) – ous acid Examples: H2SO3 (sulfite) = Sulfurous acid HNO2 (nitrite) = Nitrous acid H3PO3 (phosphite) = Phosphorous acid

Remember… ate  ic ite - ous

Writing formulas for acids Look at the charge of the anion, and add Hyrogen ions (1+) to cancel it out Example: Carbonic acid Acid ends in –ic, so anion ends in –ate Anion = carbonate (CO32-) Formula = H2CO3

Examples Hydrobromic acid HBr Chloric acid HClO3

More examples H2SO3 H2CO3 HF Nitrous acid Perchloric acid Iodic acid Sulfurous acid Carbonic acid Hydrofluoric acid HNO2 HClO4 HIO3

Mixed examples (remember to figure out what type of compound it is 1st KClO2 CO2 H2SO4 NH4Br CuCO3 Fe2O3 HClO Potassium chlorite Carbon dioxide Sulfuric acid Ammonium bromide Copper (II) carbonate Iron (III) oxide Hypochlorous acid

More Mixed Examples Carbon tetrachloride Phosphorous pentachloride Aluminum oxide Copper (II) nitrate Chlorous acid Hydrophosphoric acid Iron (III) hydroxide CCl4 PCl5 Al2O3 Cu(NO3)2 HClO2 H3P Fe(OH)3