1. Polyatomic ions

2. Li loses 1 e- becomes Li+ F gains 1 e- becomes F- • Ions • Li F • 3P 3P 4N 9P 10N

3. Ions Li+ F- Negative ion Atom has gained 1 or more electron More electrons than protons Same number of protons Negative net charge Positive ion • Atom has lost 1 or more electron • Less electrons than protons • Same number of protons • Positive net charge 9P 10N 3P 4N

4. Ions

5. Polyatomic Ions • Poly: Greek “polus” (many) • Many Atoms • Chemical Bond: Union of two or more atoms through the transfer or sharing of one or more electrons Polyatomic ion: Group of two or more chemically bonded atoms that has become electrically charged by losing or gaining one or more electrons.

6. Polyatomic ions • Na2SO4 2Na+ + SO42- • SO42- Polyatomic ion (Sulphate) • 5 chemically bonded atoms: 1 S and 4 O) • Charge:2- therefore, two extra electrons • Can you draw it using Lewis notation???  • See Table 2.10 on your Textbook (Chapter 2, Page 44) for more examples

7. Nomenclature

8. Nomenclature Chemical Formula • Symbolic representation of a molecule • Identify which elements are part of the molecule • Indicates how many atoms of each element are present

9. Nomenclature Rules for writing the chemical formula • First, Symbol of elements (Who’s there?!) • Then, Order of symbols (How are they ordered?!) (page 48 details) • Finally, Add subscripts to each symbol (How many?!)

10. Nomenclature Rules for writing the chemical formula • Subscripts: # Bonds = Noble gas configuration Group I: 1 bond (H as well) Group II: 2 bonds Group III: 3 bonds Group IV: 4 bonds Group V: 3 bonds Group VI: 2 bonds Group VII: 1 bond Example: BeCl2 Cl ▪ ▪ Be ▪ ▪ Cl

11. Nomenclature Rules for nomenclature For binary compounds: • Name the first element • Change the name of the second according to Table 2.17 (page 50) • Add, when applicable, a prefix or prefixes to specify the number of atoms of each element

12. Nomenclature Rules for nomenclature Examples: ClF3 • ClorineTrifluoride P2S3 • Diphosphorustrisulphide CO • Carbon Monoxide CO2 • Carbon Dioxide

13. Nomenclature Rules for nomenclature In ionic compounds: • Positive ion precedes the negative • Numerical prefixes (Table 2.18, page 50) are not used Examples: KI Potassium Iodide K2S Potassium Sulphide

14. Nomenclature Rules for nomenclature In ionic compounds: • Positive ion precedes the negative • Numerical prefixes (Table 2.18, page 50) are not used • Oxidation states, when variables, are to be mentioned Examples: KI Potassium Iodide K2S Potassium Sulphide CuS Copper (II) Sulphide Cu2S Copper (I) Sulphide

15. Nomenclature Rules for nomenclature In covalent compounds: • Positive valence precedes the negative • Numerical prefixes (Table 2.18, page 50) are to be used Examples: N2O4 DinitrogenTetroxide CF4 Tetrafluorine Carbon

16. Excercise Handout