Ions

1. Ions Atoms of an element with different numbers of electrons are called ions: • ions with more electrons than the atom are negatively charged and called anions. • ions with fewer electrons than the atom are positively charged and called cations. atomion symbol 23Na 23Na+ name sodium sodium ion atomic number 11 11 (Z) mass number 23 23 (A) protons 11 11 neutrons 12 12 electrons 11 10

2. Ionic Compounds • Chemistry happens among the valence electrons! • Bonds occur between atoms as a result of interactions among the valence electrons. • When the interaction is to strip electrons, the bond is said to be ionic and the entity formed is an ionic compound. • How do I recognize an ionic compound? Compounds between metals and nonmetals tend to be ionic. (Nonmetals strip electrons from metals to form the anions.) This is a crystal of NaCl. Na+ Cl- NaCl formula unit AND empirical formula

3. Ionic Compounds • Ionic compounds are made of cations and anions, held together by electrostatic attraction: • opposite electrical charges attract each other (like electrical charges repel each other) • Ionic compounds do not exist as discrete molecules, but as structured aggregates (crystals). • In NaCl, an ionic compound, Na exists as Na+ and Cl exists as Cl-. • The overall charge of an ionic compound is ZERO!

4. Ionic Charges – Monatomic Ions • Metal ions typically have a positive charge. • Group 1A metals always have a +1 charge: • Li+, Na+, K+, etc. (H is mostly H+ but can form H-) • Group 2A metals always have a +2 charge: • Mg2+, Ca2+, Ba2+, etc. • Some metal ions (usually transition metals) can have more than one charge: • Fe2+, Fe3+, Cu2+, Cu+ • Nonmetal ions typically have a negative charge. • Group 7A nonmetals typically have a -1 charge: • F-, Cl-, Br-, etc. • Group 6A metals typically have a -2 charge: • O2-, S2-, Se2-, etc. !!! Knowing what the Groups mean and knowing where the metal/nonmetal boundary is on the periodic table is a BIG help when dealing with ions and ionic compounds !!!

5. Polyatomic Ions • A group of atoms that is covalently bonded yet still has a charge is a polyatomic ion. • NO3- • SO42- • PO43- • ClO2- • etc. 3- O O P O O phosphate ion

6. Inorganic Nomenclature • molecular compounds(contain covalent bonds, generally formed between nonmetals) • ionic compounds(contain ionic or ionic and covalent bonds, generally formed between metals and nonmetals) • hydrates • acids • oxoacids • acid salts

7. Naming Binary Molecular Compounds • Name the element farthest to the left on the periodic table. (Exception: O is written last unless it’s bonded to F.) • If both elements are in the same group, name the lower one first. • Give the ion name of the second element (-ide ending). • Greek prefixes give the number of each atom in the formula. • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

8. Naming Ionic Compounds • Name the cation (metal or NH4+). • Name the anion (nonmetal or polyatomic anion). • Name monatomic (nonmetal) anions by replacing the end of the nonmetal with –ide. • oxygen becomes oxide • fluorine becomes fluoride • sulfur becomes sulfide • Memorize the names of the polyatomic anions. • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts NaCl NH4I Ba3P2 KCN sodium chloride ammonium iodide barium phosphide potassium cyanide

9. Naming Metal Ions When More Than One Ion is Possible Two methods • Stock system (Roman numeral shows the charge of the cation) • Fe2+ is iron(II) • Fe3+ is iron(III) • Sn2+ is tin(II) • Sn4+ is tin(IV) • Classic (-ic, -ous) system • -ic is for the ion with the higher charge • -ous is for the ion with the lower charge • Fe2+ is ferrous • Fe3+ is ferric • Sn2+ is stannous • Sn4+ is stannic • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

10. Naming Polyatomic Ions and Polyatomic Oxyanions • Polyatomic ions – memorize them! (examples are CN-, NH4+, OH-, O22-, SCN-, SO42-, SO32-) • Polyatomic oxyanions* are methodically named: • sulfate: SO42- (higher oxidation number) • sulfite: SO32- (lower oxidation number) • perchlorate: ClO4- • chlorate: ClO3- • chlorite: ClO2- • hypochlorite: ClO- • You must memorize these, too! • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

11. Naming Ionic Compounds - Examples MgCl2 CuCO3 CuNO3 KIO4 (NH4)3PO4 magnesium chloride copper(II) carbonate or cupric carbonate copper(I) nitrate or cuprous nitrate potassium periodate ammonium phosphate • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

12. Writing Formulas for Ionic Compounds The overall ionic compound MUST BE ELECTRICALLY NEUTRAL. One way to determine the formula for the compound formed between Ca and P is to make the charge of the cation the subscript of the anion, and vice versa: 2+ 3- Ca P Ca3P2 This method CAN get you into trouble if you’re not paying attention! potassium fluoride magnesium oxide ammonium sulfide titanium(II) nitride lead(IV) phosphate aluminum hydroxide KF MgO (NH4)2S Ti3N2 Pb3(PO4)4 Al(OH)3 • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

13. Naming Hydrates • Hydrates are ionic compounds with a specific number of water molecules attached. • Name the ionic compound, use the Greek prefix to indicate the number of waters of hydration, and end with the word “hydrate.” • CuSO4•5H2O copper(II) sulfate pentahydrate • BaCl2•2H2O barium chloride dihydrate • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

14. Naming “Binary” Acids (Acids with an Anion Name Which Ends in –ide) • NOT IN SOLUTION, the name of the acid is just the name of the binary molecular compound: • HCl(g) is hydrogen chloride • IN SOLUTION, • replace hydrogen with hydro- • change –ide to –ic • add the word “acid” • HCl(aq) is hydrochloric acid • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

15. Naming Ternary (Oxoacids) Acids (Acids with an Anion That Ends in –ate or -ite) Modify the oxyanion name: • -ate anion becomes –ic • nitrate becomes nitric • -ite anion becomes –ous • nitrite becomes nitrous sulfate: SO42- H2SO4 sulfite: SO32- H2SO3 perchlorate: ClO4- HClO4 chlorate: ClO3- HClO3 chlorite: ClO2- HClO2 hypochlorite: ClO-HClO sulfuric acid sulfurous acid • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts perchloric acid chloric acid chlorous acid hypochlorous acid

16. Naming Acid Salts • An acid salt is a polyprotic acid (an acid with more than one H) that has been only partially neutralized. • if H2X is the acid, the acid salt is MHX, where M is a cation. • NaHSO4 is an acid salt. • sodium hydrogen sulfate • sodium bisulfate • if H3X is the acid, the acid salts are MHX and MH2X. • Na2HPO4 is an acid salt. • sodium hydrogen phosphate • NaH2PO4 is also an acid salt • sodium dihydrogen phosphate • Naming inorganic compounds: • molecular compounds • ionic compounds • hydrates • acids • oxoacids • acid salts

17. Names of Common Chemicals See separate powerpoint file.

18. Names of Common Chemicals You are also responsible for knowing the names and formulas of all chemicals you encounter in your laboratory experiments.