Naming Chemical Compounds

Review What is a chemical formula? shorthand representation of the composition of a substance using atomic symbols and numerical subscripts can represent a molecule (covalent bonded structure) or a formula unit (ionic bonded structure)

Review Significance of a chemical formula formula tells number and type of atoms in a molecule or formula unit (one atom difference can cause change in properties) Examples: Ag, NaCl, HCl, Al2(SO4)3, CaSO4  5 H2O, etc.

Naming Ionic Compounds Binary ionic compounds Metal named first Name of non-metal has –ide added If metal has more than one possible charge use stock system (Roman numerals) or common name Ex: NaCl, KI, FeF2, FeF3

Naming Ionic Compounds Compounds with polyatomic ions Cation is named first (using stock or common name) Anion is named second (using name of polyatomic ion) Al2(CO3)3, BaSO4, CaSO3, Fe(NO3)2, NH4Cl (DO NOT change endings of polyatomic ions!!!)

Naming Ionic Compounds Hydrates ionic compounds that absorb water into their structures named like regular ionic compounds, add numeric prefix and hydrate at the end

Naming Ionic Compounds Prefixes: 1: mono- 2: di- 3: tri- 4: tetra- 5: penta- 6: hexa- 7: hepta- 8: octa- 9: nona- 10: deca-

Naming Ionic Compounds Hydrates ionic compounds that absorb water into their structures named like regular ionic compounds, add numeric prefix and hydrate at the end MgSO4  7 H2O, CuSO4  5 H2O

Naming Molecular Compounds Binary molecular compounds Element from left-most part of table is named first Name of second element has –ide added Use Greek prefixes to indicate number of atoms

Naming Molecular Compounds Prefixes: 1: *mono- (*only with second element) 2: di- 3: tri- 4: tetra- 5: penta- 6: hexa- 7: hepta- 8: octa- 9: nona- 10: deca-

Naming Molecular Compounds Binary molecular compounds Element from left-most part of table is named first Name of second element has –ide added Use Greek prefixes to indicate number of atoms CO, CCl4, N2O, N2O3

Naming Molecular Compounds Acids when in water, produce H+ ions, name usually from characteristic anion Hydro acids: hydro + name of halogen + -ic + acid HCl, HF, HBr Oxoacids: polyatomic ion + acid (use –ous and –ic as needed, -ic goes with > # O atoms) H2SO4, HNO2, HNO3

Naming Chemical Compounds Given: Chemical Formula Wanted: Name of Compound Need to ask questions to determine which naming rules to use Here is one set of questions you could use…

Has a metal? Yes No No Yes No Yes Yes No Yes No

Writing Formulas Use the criss-cross method – the charges (superscripts) go to the bottom (as subscripts) and switch from right to left

Writing Formulas Examples: Fe3+ + Cl1- becomes Al3+ + O2- becomes Sn2+ + O2- becomes Mg2+ + (OH)1- becomes NH41+ + SO42- becomes FeCl3 Al2O3 SnO Mg(OH)2 (NH4)2SO4

Writing Formulas Remember: you are looking for the smallest whole-number ratio of ions that will give an overall charge of 0 – that’s why the 3rd example has no subscripts (2+ +2- = 0)