1 Chemical Formulae Ionic versus Molecular/Covalent – Ionic compounds typically feature a metal (cation) and a nonmetal (anion). – Molecular compounds are composed of nonmetals exclusively. – Both must be electrically neutral in charge. – Nomenclature (naming) has similarities… the differences occur because of the law of multiple proportions. The same elements can make multiple, different compounds... Roman numerals or prefixes are used.

2 Molecular Formulae Formula Structure – Elements present – Subscripts * (shows how much of each element) CO 2 * If no subscript is present it means that there is only one atom of that element This is a molecule of a molecular compound. This is carbon dioxide.

3 carbon dioxidecarbon oxygen Molecular Nomenclature Naming Rules – Write the names of both elements. You will only learn covalent naming for binary compounds – Change the ending of the second element to - ide. – Add prefixes to each element to indicate the subscripted number of atoms present. If the first element only has one atom then no prefix is added. Example: CO 2 becomes carbon oxidecarbon dioxide

4 Molecular Nomenclature Prefixes - Greek prefixes used… 1. mono- 2.di– 3.tri- 4.tetra- 5.penta- 6.hexa- 7.hepta- 8.octa- 9.nona- 10.deca- - The final “o” or “a” of the prefix is usually dropped when preceding an element beginning with a vowel.

5 As 2 Se 3 diarsenic triselenide As 4 S 4 tetraarsenic tetrasulfide AsF 3 arsenic trifluoride AsF 5 arsenic pentachloride AsI 3 arsenic triiodide As 2 O 3 diarsenic trioxide As 2 O 5 diarsenic pentoxide As 2 S 3 diarsenic trisulfide AsCl 3 arsenic trichloride B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide AsBr 3 arsenic tribromide As 2 S 5 diarsenic pentasulfide As 2 Se diarsenic monoseleni de

6 B 2 Cl 4 diboron tetrachloride Molecular Compound Formulae (Molecules) B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Go To Next Slide BBr 3 boron tribromide BF 3 boron trifluoride BN boron nitride B 2 O 3 diboron trioxide BCl 3 boron trichloride B 4 C tetraboron monocarbide

7 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide CF 4 carbon tetrafluoride CO carbon monoxide CO 2 carbon dioxide CSe 2 carbon diselenide CCl 4 carbon tetrachloride CN 4 carbon tetranitride CI 4 carbon tetraiodide CS 2 carbon disulfide

8 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide ClF chlorine monofluorid e ClF 3 chlorine trifluoride ClO 2 chlorin e dioxide Cl 2 O dichlorin e monoxid e Cl 2 O 7 dichlorine heptoxide

9 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide GeCl 2 germanium dichloride F 2 O fluoride monoxide H 2 O dihydrogen monoxide F 2 O 2 fluoride dioxide GeCl 4 germanium tetrachlorid e GeF 4 germanium tetrafluoride ICl iodine monochlorid e ICl 3 iodine trichloride IF 5 iodine pentafluorid e IF 7 iodine heptafluorid e I 2 O 5 diiodine pentoxide

10 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide NCl 3 nitrogen chloride NF 3 nitrogen fluoride NH 3 nitrogen trihydride NO nitrogen monoxide NO 2 nitrogen dioxide N 2 O dinitrogen monoxide N 2 O 5 dinitrogen pentoxide N 4 S 4 tetranitrogen tetrasulfide N 4 Se 4 tetranitrogen tetraselenide

11 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide PCl 3 phosphorus trichloride PCl 5 phosphorus pentachloride PF 3 phosphorus trifluoride PF 5 phosphorus pentafluoride PH 3 phosphorus trihydride P 2 O 3 diphosphorus trioxide P 2 O 5 diphosphorus pentoxide P 2 S 5 phosphorus pentasulfide P 2 Se 5 diphosphorus pentaselenide P 4 S 3 tetraphosphoru s trisulfide P 4 Se 3 tetraphosphoru s triselenide

12 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide S 2 Cl 2 disulfur dichloride SF 4 sulfur tetrafluoride SF 6 sulfur hexafluoride SO 2 sulfur dioxide SO 3 sulfur trioxide Se 2 Cl 2 diselenium dichloride SeCl 4 selenium tetrachloride SeF 4 selenium tetrafluoride SeO 2 selenium dioxide SeS 2 selenium disulfide

13 B 3+ C 4+ C 4- C 2+ C 2- N 3+ N 3- N 5+ N 4+ N 2+ O 2- O 1- F 1- Si 4+ Si 2+ P 5+ P 3+ P 3- S 6+ S 4+ S 2+ S 2- Cl 1+ Cl 1- Cl 7+ Cl 5+ Cl 3+ As 3+ As 3- As 5+ Se 4+ Se 6+ Se 2- Br 1+ Br 1- Br 7+ Br 5+ Br 3+ Te 4+ Te 6+ Te 2- I 7+ I 5+ I 1+ I 1- At 1+ At 1- At 7+ At 5+ At 3+ Molecular Compound Formulae (Molecules) Go To Next Slide SiC silicon monocarbide SiCl 4 silicon tetrachloride SiF 4 silicon tetrafluoride Si 3 N 4 trisilicon tetranitride SiO silicon monoxide SiO 2 silicon dioxide SiS 2 silicon disulfide TeCl 2 tellurium dichloride TeCl 4 tellurium tetrachloride TeI 4 tellurium tetraiodide