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Chapter 9 Chemical Names and Formulas

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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

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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?

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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?

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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

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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 electrons from the 5p subshell AND two electrons from the 5s subshell to achieve full stability Naming Ions

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

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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

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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

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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

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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

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Another wayjust 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

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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

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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 cant name them like we did with ionic compounds We need prefixesprefixes tell us how many atoms of each element are present in each molecule Naming and Writing Formulas for Molecular Compounds

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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

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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 P2O3P2O3 Ex: iodine heptafluoride IF 7 Naming and Writing Formulas for Molecular Compounds