Chapter 4

Binary compounds Binary (ionic) compounds formed from a metal and non- metal –Example NaCl formed from Na + (a metal) and Cl - (a non-metal) 2 types of compounds are possible depending on the type of metal used –Type I: The metal forms only 1 type of cation –Type II: The metal can form 2 or more types of cations Naming binary compounds – ALWAYS name the cation first and then the anion

Sample Type 1 binary compounds KI, K +, I - (potassium iodide) CaS, Ca 2+, S 2- (calcium sulfide) CsBr Cs +1, Br - (Cesium bromide) MgO ??, ?? (??) CsF ??, ?? (??) AlCl 3 ??, ?? (??) MgI 2 ??, ?? (??)

Figure out the formula Rubidium oxide – must have the rubidium cation and oxide. –Rubidium is Rb + –Oxide is O 2- –So rubidium oxide must be Rb 2 O What are the formulas for Strontium iodide, and potassium sulfide?

Type II binary compounds Transition metals can form more than 1 type of cation We use roman numerals to specify the charge on transition metals. What is the charge on Fe in the compoundFeCl 2 ? The name of this cation is iron (II). The roman numeral tells us the charge on the transition metal.

Naming of Binary type II compounds We name Type II compounds the same way as Type I in that we name the compound by cation first and then anion The difference in naming is that we use a roman numeral to indicate the charge of the cation FeCl 2 is iron (II) chloride

Try to name these compounds Na 2 O CoBr 2 Al 2 O 3 CrCl 3 sodium oxide NOT sodium (I) oxide cobalt (II) bromide Aluminum oxide NOT aluminum (III) oxide chromium (III) chloride

Name to formula When trying to figure out the formula, always write out the ions just as with Type I compounds. Chromium (VI) oxide = Cr +6 O 2-, so the shortcut gives us Cr 2 O 6, but be sure to reduce if possible! CrO 3

systematic name and older name

Try for yourself Manganese (IV) oxide =?? Lead (IV) chloride = ?? Iron (III) oxide = ?? MgO 2 PbCl 4 Fe 2 O 3 (RUST)

Binary Type III compounds Type III compounds are molecular and ALWAYS have 2 non-metals bonded together Rules –1. First element in formula is named first –2. The second element is named as though it were an anion (root + -ide) –3. Use prefixes to denote the number of atoms –4. prefix mono- never used for first element!

binary Type III prefixes –mono- (1) –di- (2) –tri- (3) –tetra- (4) –penta- (5) –hexa- (6)

Examples of type III compounds CO = carbon monoxide CO 2 = carbon dioxide BF 3 = Boron trifluoride NO = nitrogen monoxide

You try! CCl 4 Na 2 O NaCl NO 2 CoBr 2 SiO 2 PCl 5 N 2 O 3 Carbon tetrachloride sodium oxide sodium chloride nitrogen dioxide cobalt (II) bromide silicon dioxide phosphorus pentachloride dinitrogen trioxide

Tips for naming binary compounds 1. Ask yourself is there a metal in the compound? –2. If yes, ask if the metal is a transition metal –3. If yes, use crossover method backwards and be sure to use roman numerals!

name to formula If there are prefixes in the name, use those to guide how many of each element you have Ex. sulfur dioxide (SO 2 ) If there are no prefixes write out the ion for each part of the name. Then use the crossover method to put the compound together lithium oxide (Li +, O 2-, Li 2 O)

Try for yourself magnesium chloride tin (IV) chloride oxygen difluoride aluminum oxide chromium (II) oxide barium nitride

Let’s try again! 1. IF 5 2. FeBr 3 3. ZnO 4. SeO 2 5. PbO 6. CrBr 3 iodine pentafluoride iron (III) bromide zinc (II) oxide selenium dioxide lead (II) oxide chromium (III) bromide

Naming compounds with polyatomic ions oxyanion – polyatomic ion with oxygen in it. Naming for compounds with polyatomic ions are essentially same as naming binary compounds When a metal is present that forms more than one ion (transition metals) use roman numerals to indicate the charge of the ion.

Naming compounds with polyatomic ions Always put the cation first and then anion. If there is more than 1 of a polyatomic ion, be sure to put the polyatomic ion in parentheses. What is the name of the compound formed from sodium and carbonate? sodium = Na + carbonate is CO 3 2- Just as before, write the cation first and then the anion Na +1 CO 3 2-

Single polyatomic ion Na +1 CO 3 2- Na 2 CO 3 sodium carbonate

Multiple of polyatomic ion Compound formed from calcium and nitrate Ca +2 NO 3 -1 Ca(NO 3 ) 2 calcium nitrate