CHAPTER 3 Ionic Compounds General, Organic, & Biological Chemistry Janice Gorzynski Smith

1. CHAPTER 3 Ionic Compounds General, Organic, & Biological Chemistry Janice GorzynskiSmith

2. CHAPTER 3: Ionic Compounds • Learning Objectives: • Octet Rule & Predicting ionic Charges • Ionic Bonds • Formation of cations by metals • Formation of anions by nonmetals • Metals capable of forming multiple charges • Formation of electronically neutral ionic compounds • Polyatomic ions • Naming Ionic Compounds • Properties of Ionic Compounds • High Melting & Boiling Points • Conductive aqueous solutions Smith. General Organic & Biolocial Chemistry 2nd Ed.

3. Bonding Definition • Bondingis the joining of two atoms in a stable • arrangement. • Elements will gain, lose, or shareelectrons to reach the electron configuration of the noble gas closest to them in the periodic table. • There are two different kinds of bonding: • Ionic bonds result from the transfer of electrons • from one element to another. • Covalent bonds result from the sharing of • electrons between two atoms. Smith. General Organic & Biolocial Chemistry 2nd Ed.

4. Bonding Definition Li F

5. Bonding Ionic Bonds vs Covalent Bonds • Ionic bonds form between: • A metal (left side periodic table) • A nonmetal (right side periodic table) Covalent bonds are formed when two nonmetals combine, or when a metalloid bonds to a nonmetal. Smith. General Organic & Biolocial Chemistry 2nd Ed.

6. Ions Cations Cationsare positively charged ions. A cationhas fewer electrons (e−) than protons. the sodium atom the sodium ion Smith. General Organic & Biolocial Chemistry 2nd Ed.

7. Ions Anions Anionsare negatively charged ions. An anion has more e− than protons. the chlorine atom the chlorine ion Smith. General Organic & Biolocial Chemistry 2nd Ed.

8. Ions The Octet Rule The octet rule: a main group element is especially stable when it possesses an octetof e− in its outer shell. octet = 8 valence e− Smith. General Organic & Biolocial Chemistry 2nd Ed.

9. Ions Charge as Determined by Periodic Group the cation charge = the group number group 1A: M 1 valence e− M+ + e− M 2 valence e− M2+ + 2e− group 2A: M 3 valence e− M3+ + 3e− group 3A: Smith. General Organic & Biolocial Chemistry 2nd Ed.

10. Ions Charge as Determined by Periodic Group the anion charge = 8 – group number group 6A: X 6 valence e− + 2e− X 2− charge = 8 – 6 = 2 group 7A: X 7 valence e− + e− X − charge = 8 – 7 = 1 Smith. General Organic & Biolocial Chemistry 2nd Ed.

11. Ions Main Group Ions Smith. General Organic & Biolocial Chemistry 2nd Ed.

12. Ions Metals with Variable Charges Smith. General Organic & Biolocial Chemistry 2nd Ed.

13. Ions Biologically Relevant Ions Smith. General Organic & Biolocial Chemistry 2nd Ed. http://www.drcruzan.com/Chemistry_PeriodicTable.html

14. Ionic Compounds Definition & Solid Structure • The sum of the charges in an ionic compound must • be zero overall. • Ions will arrange to maximize anion-cation attractions and minimize anion-anion and cation-cation repulsions Smith. General Organic & Biolocial Chemistry 2nd Ed.

15. Ionic Compounds Charge Balance Smith. General Organic & Biolocial Chemistry 2nd Ed.

16. Ionic Compounds Formula for Ionic Compounds HOW TO Write a Formula for an Ionic Compound Identify which element is the cation and which is the anion. Step [1] Determine how many of each ion type is needed for an overall charge of zero. Step [2] • When the cationand anion have different charges, use the ion charges to determine the number of ions of each needed. To write the formula, place the cation first and then the anion, and omit charges. Step [3] Smith. General Organic & Biolocial Chemistry 2nd Ed.

17. Ionic Compounds Criss-Cross Rule “Criss-cross” rule • Make magnitude of charge on one ion into subscript for other • When doing this, make sure that subscripts are reduced to lowest whole number. Al3+ O2– Al2O3 Smith. General Organic & Biolocial Chemistry 2nd Ed.

18. Naming Main Group Cations Main group cationsare named for the element from which they are formed. Na+ K+ Ca2+ Mg2+ calcium sodium potassium magnesium Smith. General Organic & Biolocial Chemistry 2nd Ed.

19. Naming Multiple Charge Cations Systematic name: Follow the name of the cation by a Roman numeral in parentheses to indicate its charge. Fe2+ Fe3+ iron(III) iron(II) Common name: Use suffix “-ous” for the cation with a smaller charge and suffix “-ic” for the cation with a higher charge. Fe2+ Fe3+ ferrous ferric Smith. General Organic & Biolocial Chemistry 2nd Ed.

20. Naming Anions Anions are named by replacing the ending of the element name by the suffix “-ide.” Smith. General Organic & Biolocial Chemistry 2nd Ed.

21. Naming Ionic Compounds • Name the cationand then the anion. • Do not specify the charge on the ion. • Do not specify how many ions of each type are needed to balance charge. Na+ sodium F− fluoride NaF sodium fluoride + Mg2+ magnesium + MgCl2 magnesium chloride Cl− chloride Smith. General Organic & Biolocial Chemistry 2nd Ed.

22. Naming Ionic Compounds HOW TO Name an Ionic Compound Determine the charge on the cation. Step [1] Step [2] Name the cationand the anion • If the cationcould be multiple charges indicate the charge with roman numerals or with a –ous / -ic suffix. Write the name of the cation first then the name of the anion Step [3] Smith. General Organic & Biolocial Chemistry 2nd Ed.

23. Naming Ionic Compounds HOW TO Derive the Formula from the Name of an Ionic Compound Identify the cationand the anion. Step [1] Step [2] Determine the charge on the cationand anion. Balance the charges. Step [3] Write the formula with the cationfirst and use subscripts to communicate charge balance. Step [4] Smith. General Organic & Biolocial Chemistry 2nd Ed.

24. Properties Physical Properties of Ionic Compounds • Ionic compounds are crystalline solids with very high melting and boiling points. • When ionic compounds dissolve in water, they • separate into cationsand anions, increasing the conductivity of the solution. +  solution NaCl water

25. Polyatomic Ions Definition A polyatomic ion is a cation or anion that contains more than one atom. The multiple atoms are held together with covalent bonds The molecule has an overall charge associated with it. Smith. General Organic & Biolocial Chemistry 2nd Ed.

26. Polyatomic Ions Writing Formula When a cation and anion of equal charge combine, only one of each ion is needed. Na+ + NaNO2 NO2− zero overallcharge SO42− + BaSO4 Ba2+ zero overallcharge Smith. General Organic & Biolocial Chemistry 2nd Ed.

27. Polyatomic Ions Writing Formula When a cationand anion of unequal charge combine, use the ionic charges to determine the relative number of each ion that is needed. Mg2+ + Mg(OH)2 OH− zero overallcharge −1 charge means 1 Mg2+anion is needed. +2charge means 2 OH− anions are needed. Smith. General Organic & Biolocial Chemistry 2nd Ed.

28. Polyatomic Ions Naming Ionic Compounds The same rules are followed for naming standard ionic compounds: • Name the cationand then the anion. • Do not specify the charge on the ions. • Do not specify how many ions of each type are • needed to balance charge. • Use –ite suffix if 1 or less Oxygen atoms in anion • Use –ate suffix if more Oxygen atoms in anion • Use bi- prefix or write hydrogen if H part of anion NaHCO3 Al2(SO4)3 sodium bicarbonate aluminum sulfate Smith. General Organic & Biolocial Chemistry 2nd Ed.