GC09 Naming and Formulas

Monatomic Ions  To name a Ionic Compound or determine it’s formula you need to understand how to identify the number of electrons that are lost or gained in each atom.  Cations Atoms that lose electrons (becoming more positive) Atoms that lose electrons (becoming more positive) Lose 1 e-, atom becomes more positive by 1Lose 1 e-, atom becomes more positive by 1 Lose 2 e-, atom becomes more positive by 2Lose 2 e-, atom becomes more positive by 2 Metals in Groups 1A, 2A and 3A lose e- and form positive charges equal to their group number Metals in Groups 1A, 2A and 3A lose e- and form positive charges equal to their group number

Naming Ions  Cations The resulting name of the atom is the name of the element followed by either “ion” or “cation” The resulting name of the atom is the name of the element followed by either “ion” or “cation” Example: Magnesium Example: Magnesium Group 2: so 2 e- will be lost making the atom charge +2Group 2: so 2 e- will be lost making the atom charge +2 This is written: Mg +2This is written: Mg +2 The name is Magnesium ion or Magnesium cationThe name is Magnesium ion or Magnesium cation

Naming Ions  Anions When atoms gain electrons, they become more negative When atoms gain electrons, they become more negative Gain 1 e-: charge decreases to -1Gain 1 e-: charge decreases to -1 Gain 2 e-: charge decreases to -2Gain 2 e-: charge decreases to -2 The charge of any Group A non-metal is determined by subtracting 8 from the group number. The charge of any Group A non-metal is determined by subtracting 8 from the group number. The name of an anion is not the same as the element name The name of an anion is not the same as the element name Start with the stem based on the element nameStart with the stem based on the element name Add the suffix: “-ide”Add the suffix: “-ide” Add “ion” or “anion”Add “ion” or “anion”

Anions  Example: Selenium is a group 6A element Selenium is a group 6A element It’s charge will be 6-8 = -2It’s charge will be 6-8 = -2 It name will be a combination of the element and “- ide”It name will be a combination of the element and “- ide” Selenide ion or Selenide anion Selenide ion or Selenide anion Written as Se -2 Written as Se -2

Transition Metals  These metals consistently form +1, +2 or +3 cations  Many form MORE than one cation  The charge of a transition metal atom depends on the number of electrons lost  Example: Iron (Fe) If an iron atom loses 2 electrons, it will have a +2 charge If an iron atom loses 2 electrons, it will have a +2 charge It’s name will be “Iron (II) ion”, read “Iron two ion” It’s name will be “Iron (II) ion”, read “Iron two ion” It’s name is written as the symbol Fe +2 It’s name is written as the symbol Fe +2 If an iron atom loses 3 electrons, it will have a +3 charge If an iron atom loses 3 electrons, it will have a +3 charge It’s name will be “Iron (III) ion”, read “Iron three ion” It’s name will be “Iron (III) ion”, read “Iron three ion” Its’ name is written as the symbol Fe +3 Its’ name is written as the symbol Fe +3

Transition metals  Try the following (Write out the name and Symbol):  Cobalt (loses 3 e-)  Nickel (loses 2 e-)  Copper (loses 1 e-)  Copper (loses 2 e-)  K  P  Be  Zinc (loses 2-)  O  Na

Polyatomic Ions  These are groups of atoms covalently bound together, that have a positive or negative charge.  Usually in the world we deal with polyatomic ions.  When you have a polyatomic ion, you deal with it as a whole unit. You never mess with its fundamental makeup

Polyatomic Ions  You need to know these. The best way is to memorize them using flashcards.  Notice: “-ite”“-ate” “-ite”“-ate” SO 3 -2 sulfiteSO 4 -2 sulfate SO 3 -2 sulfiteSO 4 -2 sulfate NO 2 - nitriteNO 3 -, nitrate NO 2 - nitriteNO 3 -, nitrate ClO 2 - chloriteClO 3 -, chlorate ClO 2 - chloriteClO 3 -, chlorate “ite” is used to indicate less oxygen “ite” is used to indicate less oxygen How much less? You need to know!How much less? You need to know! “ate” is used to indicate more oxygen “ate” is used to indicate more oxygen

Binary Ionic Compounds  Binary means “two”  Binary compounds are made up of two ions.  To name any binary ionic compound, put the cation name first followed by the anion name.

Practice  CaI2  Na2O  KCl  NaCl  A hard one  CuCl  CuCl2  Calcium Iodide  Sodium Oxide  Potassium Chloride  Sodium Chloride  Copper (I) Chloride  Copper (II) Chloride

Writing the Formula for Binary Ionic Compounds  This is the reverse of naming.  Say you have Ca and I. How do you know how many of each atom?  First: Write the charges of each ion (remember this is after the electron is lost/ gained).

Writing Formulas: THE CRISS CROSS method  Ca +2  gives 2 e-  How do you know how many of each atom?  CaI 2 I-I-I-I-  Wants 1 e-  Use “criss cross”  Notice that the resulting formula is electrically neutral

Practice  Use criss cross to determine the compound formulas for the following pairs of elements, include the name:  Magnesium and Flourine  Sodium and Oxygen  Aluminum and Bromine  Zinc (II) and Chlorine

Formulas and Names   MgF 2, Magnesium Flouride   Na 2 O, Sodium Oxide   AlBr 3, Aluminum Bromide  ZnCl 2, Zinc (II) Chloride