Naming and Formula Writing

Chemical Formulas molecular: indicates the numbers of each atom in a compound C 6 H 12 O 6 notation with numbers & symbols to show composition of a compound

empirical: gives simplest whole- number ratio of atoms of elements CH 2 O

structural: indicates how the atoms are bonded to each other

Molecules monatomic: single atoms of the same element Ex: He, Ne, Kr, Xe, Rn (noble gases) (the 1 subscript is understood) diatomic: two atoms of the same element Ex: H 2, O 2, N 2, Br 2 more than two atoms of the same element Ex: P 4 & S 8 two or more atoms of different elements Ex: H 2 O, NH 4, CO 2

Charges on all the atoms that make up a compound must add up to zero

Crisscross method for writing the formulas of binary ionic compounds the charge of each ion becomes the subscript for the other ion (without + / - signs) use simplest whole-number subscripts Ex: calcium bromide Ca +2 + Br -1  CaBr 2 *same with polyatomic ions, but put polyatomic ion in parentheses Ex: calcium hydroxide Ca +2 + OH -1  Ca(OH) 2

Some ions can exist with different charges (Fe +2 or Fe +3 ) remember that charges must = zero look at name to figure out charge Ex: iron II chloride Fe? + Cl -1  FeCl 2

Practice Strontium oxidecalcium sulfide Potassium carbonatelead (II) sulfate Magnesium sulfidecopper (I) chlorate Strontium nitrate dihydrogen monosulfide phosphorus pentachloridecalcium chloride Sodium sulfiderubidium sulfide Iron (III) chlorate

Rules for Naming Compounds Basic Rule: 1)Name the first element in the compound 2)Name the second element by changing the ending of the name to –ide OR if the compound is made up of more than 2 elements, you have a polyatomic ion and you will use the polyatomic ion’s name with no changes

Naming a Metal and a Nonmetal Basic rule—no changes Ex: NaClsodium chloride CaSO 4 calcium sulfate

Naming Compounds with transition metals Basic rule with one change: –Find the charge of the transition metal (the charge of a transition metal can change) –Write the charge after the transition metal’s name (in Roman numerals) Ex Co I 2 cobalt (II) iodide Fe(ClO 3 ) 3 iron (III) chlorate

Naming 2 nonmetals Basic rule with one change: –Look at the number of atoms for the second nonmetal and select the correct prefix to add to the name: PrefixMeaning mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6

2 nonmetals (continued): Ex CO carbon monoxide CO 2 carbon dioxide If the 1 st element in the compound has more than one atom, a prefix must be added to the first element’s name also 2 nd elment always gets a prefix, 1 st element only gets a prefix if more than one atom Ex P 2 S 3 diphosphorus trisulfide N 2 O 5 dinitrogen pentoxide Usually you won’t have 2 vowels together –Exceptions: di-, tri-, tetra-, & penta- iodide and oxide

Practice CaSNiCl MgCl 2 SiCl 4 Zn(NO 3 ) 2 K 2 CO 3 Hg(C 2 H 3 O 2 ) 3 Li 2 SO 4 LiBrPCl 5 H 2 OPbSO 4 SrOCF 4 Ag(CrO 4 ) 2 CS 2