CHEMICAL NAMES AND FORMULAS. Nomenclature

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1 CHEMICAL NAMES AND FORMULAS Nomenclature

2 Naming Monatomic Ions Monatomic ions single atom with a (+) or (-) charge Cations Group 1A, 2A, and 3A elements Name is the same as the metal followed by the word ion or cation examples Na + - sodium ion or sodium cation Ca 2+ - calcium ion or calcium cation

3 Naming Monatomic Ions Anions Groups 5A, 6A, & 7A The name is not the same as the element s name < different from the rules for naming cations> Start with the stem of the element name and end in ide. Examples fluorine (F - ) fluoride ion oxygen (O -2 ) oxide ion Nitrogen (N -3 ) nitride ion Group 4A and 8A elements do not usually form ions Now it s your turn! Do the problems corresponding to the naming monatomic ions heading.

4 Ions of Transition Metals The charges of the cations of many transition metals must be determined by the number of electrons lost Some transition metals can more than one ion with different charges.

5 Table 9.2 Symbols Common Metal Ions with More than One Ionic Charge Symbol Cu + Cu 2+ Fe 2+ Fe 3+ Hg 2 2+ Hg 2+ Pb 2+ Pb 4+ Sn 2+ Sn 4+ Cr 2+ Cr 3+ Mn 2+ Mn 3+ Co 2+ Co 3+

6 Ions of Transition Metals There are 2 methods for naming the ions of transition metals The Stock System and the classical names The Stock System is the preferred Stock System A roman numeral in parentheses is placed after the name of the element(metal) to indicate the numerical value of the charge. Do not leave a space between the element name and the roman numeral in parentheses Example Fe 2+ iron(ii) ion should be read as iron two ion Cu 2+ copper(ii) ion copper two ion

7 Ions of Transition Metals Classical Names not the preferred method, however you must know it. Uses a root word with different suffixes at the end of the word The suffix ous is used to name the cation with the lower of the two ionic charges The suffix ic is used to name the cation with the higher of the two ionic charges. Examples ferrum is latin for iron therefore ferr- is the root of the word Fe 2+ - ferrous ion Fe 3+ - ferric ion stannous is latin for tin therefore stann- is the root of the word Sn 2+ - stannous ion Sn 4+ - stannic ion

8 Ions of Transition Metals Classical Names Disadvantages Does not tell you the actual charge Only tells you whether the cation has the smaller or larger of the charges A few transition metals have only one charge Do not use roman numerals when using the stock system Some of these exceptions are silver - Ag +, cadmium Cd 2+, & zinc 2+ Now it s your turn! Complete the section also labeled Ions of Transition Metals

9 Polyatomic Ions Composed of more than one atom The names of polyatomic anions end in ite or ate Examples Hypochlorite ClO - Hydrogen carbonate (HCO 3- ) Three common polyatomic ions have different endings Ammonium ion (NH 4+ ) Cyanide ion (CN - ) Hydroxide (OH - )

10 Polyatomic Ions Sometimes the same elements combine in different ratios to form different polyatomic ions Examine the following chart, what do you notice? -ite SO 2-3, sulfite NO 2 -, nitrite ClO 2-, chlorite -ate SO 2-4, sulfate NO 3-, nitrate ClO 3-, clorate

11 Polyatomic Ions If the formula begins with H (hydrogen) think of it as representing the hydrogen ion H + combined with another polyatomic ion. The charges of the new ion is the sum of the 2 original ion charges

12 Common Polyatomic Ions

13 Naming and Writing Formulas for Ionic Compounds

14 Binary Ionic Compounds Antoine-Laurent Lavoisier worked to identify the composition of many compounds Worked with other chemists to develop a system for naming compounds the chemical names today are based on their work Binary compound composed of two elements and can be ionic or molecular If you know the formula of an ionic compound, it is easy to write the name Place the cation name first, followed by the anion name

15 Binary Ionic Compounds For ionic compounds that contain metals with only one possible charge it is simple Cs 2 O Cs- cesium(the cation), O oxygen (the anion) cesium oxide NaBr Na sodium (cation), Br bromine (anion) sodium bromide SrF 2 Sr strontium (cation), F fluorine (anion) strontium fluoride What about elements with transition metals that can have different ionic charges? You must use the stock system or the classical name for the cation Stock System CuO copper(ii) oxide Cu 2 O copper(i) oxide How do you know which cation formed each compound? Work backwards

16 Binary Ionic Compounds CuO copper(ii) oxide Cu 2 O copper(i) oxide The formulas indicate the ratios CuO - the copper cation and the oxide anion combine in a 1:1 ratio The oxide ion always has a charge of 2- The charge of the copper cation must be 2- to balance the charge Cu 2 O the copper cation and the oxide anion combine in 2:1 ratio The oxide ion always has a charge of 2- You need to +1 cations to balance the charge

17 Binary Ionic Compounds Using the classical names for the ions SnF 2 and SnS 2 The fluoride anion has a charge of -1 and the sulfur anion has a charge of -2 SnF 2 The ratio of Sn to F is 1:2 therefore the charge of Sn must be +2 to balance the -2 charge of the two fluoride anions stannous fluoride because +2 is the lower of the ionic charges for tin SnS 2 The ratio of Sn to S is 1:2, S is a -2 so to balance the -4 charge of S anions the charge of tin must be +4 Stannic sulfide because +4 is the higher of the ionic charges for tin

18 Writing formulas for Binary Ionic Compounds If you know the name of the binary ionic compound, it is simple to write the formula Write the symbol of the cation and then the anion. Add the subscripts necessary to balance the charges. Remember the net ionic charge must = 0. Potassium chloride K + Cl - The charge of each K + is balanced by the charge of each Cl - therefore the ratio is 1:1 KCl Calcium bromide Ca +2 Br - The charge of each Ca +2 ion must combine with 2 Br - anions to balance the charges CaBr 2

19 Writing Formulas for Binary Ionic Compounds You can also use the crisscross method. The numerical value of the charge of each ion becomes the subscript for the other ion.

20 Writing Formulas for Binary Ionic Compounds

21 Compounds with Polyatomic Ions -ate or ite ending indicates a compound with a polyatomic ion that includes oxygen Writing the chemical formula requires the same process. Write the symbols and then add the subscripts necessary to balance the charge Examples Calcium carbonate Ca +2 CO 3 2-1:1 ratio CaCO 3 Calcium nitrate Ca +2 NO - 3 1:2 ratio Ca(NO 3 ) 2 Use parentheses around the polyatomic ion when more than one is required to balance the charges and place the subscript after the parentheses. The criss-cross method can also be used

22 Naming Compounds with Polyatomic Ions When given the formula 1 st recognize that the compound contains a polyatomic ion Yes it will be necessary for you to memorize the common polyatomic ions!! 2 nd state the cation first and then the anion Examples LiCN lithium cyanide NaClO sodium hypochlorite (ClO - ) this is a polyatomic ion with the name hypochlorite because it has one less oxygen than ClO 2 - which is has the name chlorite.