Bonding & Chemical Nomenclature Chapter 8 & 9

1. Bonding & Chemical NomenclatureChapter 8 & 9

2. Some Key Terms • Ionic Bond – the electrostatic attraction of oppositely charged particles (cations & anions) • Alloy – a homogeneous mixture of metals • Anion – a negatively charged ion – gained electrons to become negative • Cation – a positively charged ion – lost electrons to become positive • Electrolyte – a solution that conducts electricity • Formula unit – the simplest piece of an ionic compound

3. Key Terms cont. • Covalent bond – results from the sharing of electrons • Chemical Formula – a formula that indicates the relative #’s of atoms of each kind in a chemical compound. Uses atomic symbols and numerical subscripts. Ex. NaCl, Mg(OH)2 • Polyatomic Ion – A charged group of covalently bonded atoms. Contains two or more different elements • Polar Covalent – unequal sharing of electrons in a covalent bond

4. Key Terms cont. • Molecule – Neutral group of atoms held together by covalent bonds. • Oxidation number - # assigned to an atom in a molecular compound or ion that indicates its distribution of electrons (charge) • Octet rule – Chemical compounds tend to form so that each atom has an octet (8) electrons in the highest energy level except for a few of the smallest atoms.

5. Ionic Bonding • An ionic bond is the electrostatic attraction of oppositely charged particles (cations and anions) • It involves the transfer of electrons • Usually forms between a metal and a nonmetal • Compounds with ionic bonds are called ionic compounds or salts • An individual unit of an ionic compound is called a formula unit

6. What are ions? • Ions are atoms that have lost or gained electrons to become positively or negatively charged. • Metals tend to form positively charged ions called cations • Nonmetals tend to form negatively charged ions called anions. • To determine the charge of an ion we must look at the arrangement of VALENCE ELECTRONS.

7. Review of Lewis Dot Diagrams • Lewis dot diagrams show an elements valence electrons as dots around the element’s symbol. • To determine valence electrons for main group elements refer to the “A” group number. • REMEMBER – a valence electron is an electron in the outermost energy level

8. Formation of Ions • Label your periodic table with the following charges above each group: • Group 1A = +1 • Group 2A = +2 • Group 3A = +3 • Group 4A = +/-4 • Group 5A = -3 • Group 6A = -2 • Group 7A = -1 • Group 8A = 0

9. Polyatomic ions • A charged group of covalently bonded atoms. Contains two or more different elements • A list of these can be found on your reference sheet • A more complete list is found in your book on p. 224

10. Characteristics of Ionic Compounds • Another name for an ionic compound is salt • Crystalline solids at room temp., regular repeating 3D pattern called crystal lattice. • High melting and boiling points • Generally soluble in water • Conduct electricity when molten or in solution • Brittle

11. Covalent Bonding • Covalent bonds occur when atoms (usually 2 nonmetals) share electrons. • Molecules that contain covalent bonds are called molecular compounds. • An individual unit of a molecular compound is referred to as a molecule

12. Characteristics of Molecular Compounds (covalent) • Found as amorphous solids, liquids, and gases • Low melting and boiling points • Generally only slightly soluble to insoluble in water • Generally do not conduct electricity when molten or in solution

13. Metallic Bonding • Scientists believe that pure metals are made up of closely packed cations. In these structures, electrons are free to move between atoms. This is often used to explain why metals conduct electricity. • Electron Sea Model

14. Naming Binary Ionic Involves a metal and a nonmetal • Name the metal • Name the nonmetal and change the ending to –ide. Examples NaCl K2O BaF2

15. Naming Binary Ionic with transition metals Still Metal – Nonmetal. We use this method only if the metal can have a variable charge/oxidation number. The majority of these will be transition metals. Exceptions to memorize: Silver (Ag+1), cadmium (Cd+2), zinc (Zn+2) • Name the metal • Using a roman numeral write the oxidation number of the metal in parenthesis. To get the oxidation number uncriss-cross the charges. • Name the nonmetal and change the ending to –ide Examples CuBr2 Fe2O3 FeO

16. Naming Ionic with Polyatomic Ions • Name the metal • Name the polyatomic ion • Be sure to use a roman numeral if it is necessary (transition metals) Examples LiNO3 KMnO4 Na2CO3 FeSO4

17. Writing Formulas for Ionic Compounds • Write the symbol and charge for the metal (if it is a transition metal use the Roman Numeral in the name for the charge) • Write the symbol and charge for the nonmetal or polyatomic ion. • Criss-cross the charges to form the neutral compound Ex. Sodium chloride Magnesium phosphate Gold (III) chloride

18. Naming Binary Molecular (covalent) Compounds Involves a bond b/w 2 nonmetals • Name the 1st nonmetal. Use a prefix if there is more than one. • Name the 2nd nonmetal ALWAYS use a prefix. Change the ending to –ide. Examples NO P2O5 SO3 Prefixes 1 mono- 6 hexa- 2 di- 7 hepta- 3 tri- 8 octa- 4 tetra- 9 nona- 5 penta- 10 deca-

19. Writing Molecular (covalent) compounds • Write the symbol for each nonmetal • Write a subscript on the right of each metal according to the prefix it has in the name. If there is not a prefix then no subscript is needed. Ex. carbon dioxide dinitrogen pentaoxide nitrogen monoxide

20. Naming Binary Acids • Acids generally start with Hydrogen • Binary Acids (H with one element) • Use the prefix hydro- • Then add the name of the second element and change the ending to –ic acid • HCl hydrochloric acid • HBrhydrobromic acid • HI hydroiodic acid

21. Naming Acids with Polyatomic Ions • Hydrogen with a polyatomic ion (group of atoms with a charge) • Identify the polyatomic ion • Change the ending accordingly: • -ate to –ic acid • -ite to -ous acid • (Do NOT use the prefix Hydro-) • H2SO4 sulfuric acid • HNO3 nitric acid • HNO2 nitrous acid