Unit 7 Naming and Formulas Chapter 9-10

Ionic Compounds Ionic compounds are electrically neutral, even though they are composed of charged ions Total positive charge equals total negative charge

Determining Formulas Must be electrically neutral Total positive charge must equal total negative charge Use oxidation numbers from Periodic Table Group 1  +1Group 2  +2 Group 13  +3Group 15  -3 Group 16  -2Group 17  -1

Determining Formulas Determine number of each ion to balance out charge Use as subscript for element symbol Ex: CaCl 2, Na 3 PO 4, Mg(NO 3 ) 2 Write Positive Ion First Formula must be smallest whole- number ratio

Example Sodium and Chlorine Na + Cl - Na 1 Cl 1 NaCl

Example Calcium and Fluorine CaF 2 Ca +2 F-F- F-F- Ca 1 F 2

Examples Potassium and Oxygen K2OK2O K+K+ O -2 K+K+ K2O1K2O1

Polyatomic Ions Group of atoms that collectively have gained or lost electrons (Table E) Sodium and Nitrate Na + (NO 3 ) - Na 1 (NO 3 ) 1 NaNO 3

More Examples Potassium and Sulfate Ammonium and Sulfur K 2 SO 4 (NH 4 ) 2 S

Short-cut (criss-cross method) Magnesium and Phosphate Mg 3 (PO 4 ) 2 Mg +2 PO 4 -3

Short-cut (criss-cross method) Magnesium and Carbonate Mg 2 (CO 3 ) 2 Mg +2 CO 3 -2 MgCO 3 Must Simplify

Naming Ions Positive Ions, cations, simply retain their name. Na +  Sodium Ion Mg 2+  Magnesium Ion

Naming Ions Negative Ions, anions, change ending of element to –ide Cl -  Chloride Ion Br -  Bromide Ion

Unique Anions Names N 3-  Nitride Ion O 2-  Oxide Ion S 2-  Sulfide Ion P 3-  Phosphide Ion

Stock System Used when the metal has more than one positive oxidation number Use a roman numeral to indicate the charge of the ion

Roman Numerals Cation Charge Roman Numeral +1I +2II +3III +4IV +5V +6VI +7VII +8VIII

Stock System Examples Fe +2  Iron(II) Cu +  Copper(I) Mn +7  Manganese(VII) Au +3  Gold(III) Cr +6  Chromium(VI) Pb +4  Lead(IV)

Polyatomic Ions Selected polyatomic ions are on Table E in the Reference Tables. Polyatomic ions keep their names in most chemical names

Naming Systems Ionic System Stock System (Roman Numerals) Binary Covalent System (Prefixes)

When to use ionic system First element is a metal NaCl More than 2 elements, meaning polyatomic ion is involved NH 4 Cl

Naming Ionic Compounds Name positive ion first, then negative ion. NaCl  Sodium chloride Fe(OH) 2  Iron(II) hydroxide

Binary Covalent Compounds Use when compound is 2 nonmetals Including metalloids Use a prefix system to indicate the number of atoms for each element Second element ends in -ide

Prefixes Number of atomsPrefix 1mono- 2di- 3tri- 4tetra- 5penta- 6hexa- 7hepta- 8octa-

Example N 2 Cl 3 Dinitrogen Trichloride

Exceptions When there is only one atom of the first element, do not use mono- prefix. CO 2 Carbon dioxide OF 2 Oxygen difluoride

Exceptions When an element starts with a vowel, drop any o or a at the end of a prefix CO Carbon Monooxide Carbon Monoxide P 2 O 5 Diphosphorus Pentaoxide Diphosphorus Pentoxide