Chemical Names and Formulas Nomenclature

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 Ca2+ - calcium ion or calcium cation

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.

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.

Table 9.2 Symbols Common Metal Ions with More than One Ionic Charge Cu+ Cu2+ Fe2+ Fe3+ Hg22+ Hg2+ Pb2+ Pb4+ Sn2+ Sn4+ Cr2+ Cr3+ Mn2+ Mn3+ Co2+ Co3+

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 Fe2+ iron(II) ion  should be read as “iron two ion” Cu2+ copper(II) ion  “copper two ion”

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 Fe2+ - ferrous ion Fe3+ - ferric ion stannum is latin for tin therefore stann- is the root of the word Sn2+ - stannous ion Sn4+ - stannic ion

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 – Cd2+, & zinc2+ Now it’s your turn! Complete the section also labeled Ions of Transition Metals

Polyatomic Ions Composed of more than one atom The names of polyatomic anions end in –ite or –ate Examples Hypochlorite – ClO- Hydrogen carbonate (HCO3-) Three common polyatomic ions have different endings Ammonium ion (NH4+) Cyanide ion (CN-) Hydroxide (OH-)

Polyatomic Ions Sometimes the same elements combine in different ratios to form different polyatomic ions Examine the following chart, what do you notice? -ite -ate SO32-, sulfite SO42-, sulfate NO2-, nitrite NO3-, nitrate ClO2-, chlorite ClO3-, clorate

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

Common Polyatomic Ions

Naming and Writing Formulas for Ionic Compounds

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

Binary Ionic Compounds For ionic compounds that contain metals with only one possible charge it is simple Cs2O  Cs- cesium(the cation), O – oxygen (the anion)  cesium oxide NaBr  Na – sodium (cation) , Br – bromine (anion)  sodium bromide SrF2  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 Cu2O – copper(I) oxide How do you know which cation formed each compound? Work backwards

Binary Ionic Compounds CuO – copper(II) oxide Cu2O – 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 Cu2O – the copper cation and the oxide anion combine in 2:1 ratio You need to +1 cations to balance the charge

Binary Ionic Compounds Using the classical names for the ions SnF2 and SnS2 The fluoride anion has a charge of -1 and the sulfur anion has a charge of -2 SnF2 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 SnS2 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

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  CaBr2

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.

Writing Formulas for Binary Ionic Compounds

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 CO32-  1:1 ratio  CaCO3 Calcium nitrate Ca+2 NO3-  1:2 ratio  Ca(NO3)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

Naming Compounds with Polyatomic Ions When given the formula 1st – recognize that the compound contains a polyatomic ion Yes it will be necessary for you to memorize the common polyatomic ions!! 2nd – 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 ClO2- which is has the name chlorite.