Polyatomic ions & Naming ionic Compounds
Unit 5: Chapter 6.3a
Bonding Review Ionic - electron transfer
Forms between a metal and a nonmetal Metals have low electronegativity Nonmetals have high electronegativity The metal gives up the electrons and the nonmetal takes them Covalent - electron sharing Forms most often between two nonmetals Electron shared pairs are formed to allow both elements to fulfill the octet rule.
Describing Ionic Compounds
These objects are coated with compounds of copper and oxygen. Based on the two colors of the coatings, copper and oxygen must form at least two compounds. So there must also be different ways of naming them.
Describing Ionic Compounds
What information do the name and formula of an ionic compound provide? The name distinguishes the compound from other ionic compounds containing the same elements. The formula of an ionic compound describes the ratio of the ions in the compound.
Binary Ionic Compounds
A compound made from only two elements is a binary compound. Naming binary ionic compounds is easy. The names have a predictable pattern: the name of the cation (metal) followed by the name of the anion (nonmetal). Examples: Na+ + Cl- Sodium Ion + Chloride = Sodium Chloride K+ + O2- Potassium Ion + Oxide = Potassium Oxide
Common Anions This table lists eight common anions.
The name of an anion is formed by adding the suffix –ide to the stem of the nonmetal name.
Naming Binary Ionic Compounds
Cations (metal) first, then Anion (non-metal) Cation (metal) name is normal Example: sodium Anion (nonmetal) add “ide” suffix Example: chlorine chloride NaCl sodium chloride KBr potassium bromide
Polyvalent Metals Many transition metals have “multiple personalities”
# of valence electrons varies they can form more than one ion (more than one charge). Also known as valence # or oxidation # Roman Numerals are used to signify the charge (or how many electrons the metal is lending) Where are the transition metals located on the periodic table?
Polyvalent Transition Metals
Metals with more than one possible charge: Specific charge is indicated in parenthesis
Polyvalent Metals & Bonding
Fe(II) = Fe2+ Iron (II) + oxygen = Iron (II) Oxide Fe2+ & O2- FeO Fe(III) = Fe3+ Iron (III) + oxygen = Iron (III) Oxide Fe3+ & O2- Fe2O3 Name these compounds just like other binary ionic compounds but include the metal’s oxidation # in parentheses
Polyatomic Ions Polyatomic Ion - A covalently bonded group of atoms that acts as a unit and has its own charge. Most simple polyatomic ions are anions. MUST keep the atoms together CANNOT change anything about a polyatomic ion Not the type of atoms Not the number of atoms Not the electric charge How are you going to remember this???? Anytime you see a Polyatomic Ion PUT IT IN PARENTHESIS!!!
Polyatomic Ions & Bonding
Bonding works the same way as it did for binary compounds. Treat the polyatomic ion as a single entity (a single element) The criss cross method is the most useful, efficient, and effective way for bonding with polyatomic ions.
Criss Cross Method Review
Determine the charges/oxidation #’s for each element. By criss crossing the charges of the elements you can easily write the chemical formula Example: Hydrogen + Oxygen H O–2 Criss cross the oxidation # just the numbers - not the + / - signs Write the numbers as subscripts bottom right of symbol
Criss Cross Method Review
Criss Cross the numbers H2O1 Final: H2O Where is the 1 in the final formula? Just like in math, the 1 is always understood.
Criss Cross & Polyatomic Ions
Sodium + Sulfate Na + SO4 Na+1 + (SO4)-2 Do the Criss Cross Na2(SO4)1 Final: Na2(SO4) or Na2SO4
You Try Magnesium + Sulfate Mg + SO4
You Try Magnesium + Sulfate Mg + SO4 Mg+2 + (SO4)-2
You Try Magnesium + Sulfate Mg + SO4 Mg+2 + (SO4)-2 Criss Cross
Final: Mg(SO4) or MgSO4 Remember the ratio can be reduced! (the 2’s reduce to 1:1)
You Try Beryllium + Phosphate Be + PO4
You Try Beryllium + Phosphate Be + PO4 Be+2 + (PO4)-3
You Try Beryllium + Phosphate Be + PO4 Be+2 + (PO4)-3 Criss Cross
Note that the criss cross puts the subscript 2 OUTSIDE of the parenthesis, showing that there are TWO phosphate ions
Common Ions Which of these are: Metals? Nonmetals? Transition metals?
Hydrogen H+1 Aluminum Al+3 Nitrate (NO3)-1 Calcium Ca+2 Iron (III) Fe+3 Sulfate (SO4)-2 Zinc Zn+2 Chlorine Cl-1 Carbonate (CO3)-2 Copper (II) Cu+2 Hydroxide OH-1 Phosphate (PO4)-3 Silver Ag+1 Phosphide P-3 Acetate (C2H3O2)-1 Which of these are: Metals? Nonmetals? Transition metals? Polyatomic ions?
Naming with Polyatomic Ions
Compounds containing polyatomic Ions always have IONIC bonds. Naming these compounds is much like naming binary ionic compounds List the cation (metal) first Then the polyatomic ion (most are anions so this follows the binary format) Use the normal name for the cation (metal) and the given name for the polyatomic ion Na(OH) or NaOH = Sodium Hydroxide
Formulas & Names Use a compound’s formula to determine its name
Na2O Sodium Oxide CuF2 Copper (II) Fluoride K2(CO3) Potassium Carbonate Use a compound’s name to determine its formula Lithium Bromide LiBr Iron (III) Oxide Fe2O3 Aluminum Phosphate Al(PO4) or AlPO4 You must be able to go back and forth!
You Try Write the formula for Calcium Chloride Calcium Oxide
Copper (II) Nitride Magnesium Sulfate Give the name for the following compounds KBr BeS PbO2 CsMnO4
You Try Write the formula for Calcium Chloride CaCl2
Calcium Oxide CaO Copper (II) Nitride Cu3N2 Magnesium Sulfate MgSO4 Give the name for the following compounds KBr Potassium Bromide BeS Beryllium Sulfide PbO2 Lead (IV) Oxide CsMnO4 Cesium Permanganate
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