Polyatomic ions & Naming ionic Compounds

1. Polyatomic ions & Naming ionic Compounds Unit 5: Chapter 6.3a

2. 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.

3. 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.

4. 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.

5. 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

6. 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.

7. 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

8. 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?

9. Transition Metals

10. Polyvalent Transition Metals • Metals with more than one possible charge: • Specific charge is indicated in parenthesis

11. 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

12. 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!!!

13. Polyatomic Ions

14. 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.

15. 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+1 + O–2 • Criss cross the oxidation # • just the numbers - not the + / - signs • Write the numbers as subscripts • bottom right of symbol

16. Criss Cross Method Review H+1 O-2 CrissCross the numbers H2O1 Final: H2O • Where is the 1 in the final formula? • Just like in math, the 1 is always understood.

17. Criss Cross & Polyatomic Ions • Sodium + Sulfate • Na + SO4 • Na+1+ (SO4)-2 Do the Criss Cross Na2(SO4)1 Final: Na2(SO4) or Na2SO4

18. You Try • Magnesium + Sulfate • Mg + SO4

19. You Try • Magnesium + Sulfate • Mg + SO4 • Mg+2 + (SO4)-2

20. You Try • Magnesium + Sulfate • Mg + SO4 • Mg+2 + (SO4)-2 • Criss Cross • Mg2(SO4)2 • Final: Mg(SO4) or MgSO4 • Remember the ratio can be reduced! (the 2’s reduce to 1:1)

21. You Try • Beryllium + Phosphate • Be + PO4

22. You Try • Beryllium + Phosphate • Be + PO4 • Be+2+ (PO4)-3

23. You Try • Beryllium + Phosphate • Be + PO4 • Be+2+ (PO4)-3 • Criss Cross • Be3(PO4)2 • Note that the criss cross puts the subscript 2 OUTSIDE of the parenthesis, showing that there are TWO phosphate ions

24. Which of these are: • Metals? • Nonmetals? • Transition metals? • Polyatomic ions?

25. Naming with Polyatomic Ions • Compounds containing polyatomic Ionsalways 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

26. 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!

27. 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

28. 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