Chapter 9 Chemical Names and Formulas

 What is the difference between Cu 2 O and CuO? Is there any difference?  You may think that there is very little difference between the two, but there is! Naming compounds very specifically is important in order to tell the difference between similar compounds?  Cu 2 O  Red powder  fungicide  CuO  Black powder  Used in batteries Copper Compounds

 What is a cation?  Cations – positively charged ion  How many electrons does Group 1,2, and 3 lose?  Groups 1,2, and 3 lose electrons  Group 1 – lose 1 electron  Group 2 – lose 2 electrons  Group 3 – lose 3 electrons Remeber Naming Ions?

 Anion – negatively charged ion  Groups 5,6, and 7 generally gain electrons  Group 5 – gain 3 electrons  Group 6 – gain 2 electrons  Group 7 – gain 1 electron Remember Naming Ions?

 Transition metals usually lose electrons, how many electrons they lose depends on the element  You should memorize these metal ions – Table 9.2! Naming Ions

 If you actually think about it, it will make sense why some of the transition elements could have two different ions  Ex: Tin (Sn) forms both a +2 and a +4 cation  Why? (Hint: Use the periodic table and electron configuration.)  +2 cation: Sn = [Kr] 5s 2 4d 10 5p 2 – loses 2 from the 5p subshell  + 4 cation: Sn can lose both the 2 electron’s from the 5p subshell AND two electrons from the 5s subshell to achieve full stability Naming Ions

 Writing and naming ionic compounds.  Writing and naming covalent compounds. Learning Objective of the Day:

 Ions composed of more than 1 atom  You just have to memorize these – Table 9.3  Most end in –ite or –ate  -ite tells you there is 1 less oxygen atom than the –ate ending Polyatomic Ions

 what do ionic compounds contain?  Ionic compounds – contain a metal and a nonmetal  How do we name a binary ionic compound (binary means composed of 2 elements)?  Place the cation name first, then the anion name  Usually add –ide to the end of the anion name Naming and Writing Formulas for Ionic Compounds

 What would Cs 2 O be?  Cesium oxide  NaF?  Sodium fluoride  Cu 2 O (hint: copper has two possible ions! Which one is it?)  Copper ( I ) oxide  SnS 2  Tin (IV) Sulfide  Mn 2 O 3  Manganese (III) oxide  LiCN  Lithium cyanide  (NH 4 ) 2 C 2 O 4  Ammonium oxalate (the –ide ending is usually left out if the anion is a polyatomic ion) Naming and Writing Formulas for Ionic Compounds

 To write a formula for a binary ionic compound, we need to go back to Ch. 7 and balance the charges  Ex: iron (III) oxide  Fe +3 O -2  Fe 2 O 3  Ca +2 S -2  Ca 2 S 2 ….reduce to CaS  Remember crisscross the charge and reduce subscripts to the lowest whole number ratio Naming and Writing Formulas for Ionic Compounds

 Another way…just think about how you would balance the charges out by finding the least common multiple  K +1 N -3  We need a 3 to balance out the +1 on K (1 x 3 =3) and a 1 to balance out the -3 on N (1 x 3) = 3  So K 3 N  Ba +2 S -2  Both have a 2 charge, they balance each other out  BaS Naming and Writing Formulas for Ionic Compounds

 For polyatomic ions, keep the ion together – balance the overall charge of the ion  Ex: Ca +2 (NO 3 ) -1  Ca(NO 3 ) 2  Use parentheses to set off the polyatomic ion only if there is than one of the polyatomic ion  Ex: Li +1 (CO 3 ) -2  Li 2 CO 3 – no parentheses because there is only one polyatomic ion  Ex: NH 4 +1 (SO 3 ) -2  (NH 4 ) 2 SO 3 Naming and Writing Formulas for Ionic Compounds

 What is a binary molecular compound?  A compound composed of 2 elements that are both nonmetals – NOT ions  Binary compounds can have 2 elements composed in various ways – ex: CO and CO 2 or NO and N 2 O so we can’t name them like we did with ionic compounds  We need prefixes…prefixes tell us how many atoms of each element are present in each molecule Naming and Writing Formulas for Molecular Compounds

 Here are a few hints:  If there is only 1 atom of the first element, omit the prefix mono-  You will usually add the –ide ending to the second element  Ex: CO  Carbon monoxide  Ex: N 2 O  Dinitrogen monoxide  Ex: Cl 2 O 7  Dichlorine heptoxide  Ex: BCl 3  Boron trichloride Naming and Writing Formulas for Molecular Compounds

 Use the prefixes of each element to write the formula (hint: -mono is left out of the first element if there is only 1 atom)  Ex: carbon monoxide  CO  Ex: carbon tetrabromide  CBr 4  Ex: diphosphorus trioxide P2O3P2O3  Ex: iodine heptafluoride  IF 7 Naming and Writing Formulas for Molecular Compounds