1. Chemical Bonding and Formulas Adapted from: www.rsu.edu/faculty/mallen Available online @: www.redwood.org/stewart

2. I. Review: The periodic table of the elements. Noble Gases Non-metals Halogens Alkali Earth Metals Alkali Metals Metals 2 e- (in 1st level when stable, full) 8 e- (in 2nd level when stable, full) 8 e- (in 3rd level when stable (18 when full)) 8 e- (in 4th level when stable (32 when full)) 8 e- (in 5th level when stable (50 when full)) 8 e- (in 6th level when stable (72 when full)) 98 e- in 7th level when full Periods Families/Groups 1e- 2e-3e-4e-5e-6e-7e- 8e- (except He) # of p # of p + n

3. II. Valence Electrons and Diagrams (Review) Chemical behavior is determined by the outer electrons. These are called valence electrons Elements react so as to FILL or EMPTY their outer shell and become more STABLE. A full outer shell has 8 electrons except elements H and He (since the 1st shell has only 2 electrons). These outer shell electrons are represented using electron dot diagrams. see next slide

4. Electron dot diagrams (showing valence electrons) for the representative elements (electrons present in outer shell). Need 1 to be full Give up 1 to be empty Need 2 to be full II. Valence Electrons and Diagrams (Review)

5. III. Types of Chemical Bonds –IONIC BONDS:When an atom or molecule gains or loses an electron it forms an ionic bond (when a metal and non-metal bond). A cation has lost an electron and therefore has a positive charge. These are the metals which always tend to lose electrons. (FAMILIES 1,2,3) An anion has gained an electron and therefore has a negative charge. These are the nonmetals which always tend to gain electrons. (FAMILIES 5,6,7) metal Non- metal compound ¨ [Na]:Cl: ¨ Electron dot diagam showing how valence electrons have been transferred [brackets] ¨ Na:Cl: ¨ Each atom has 0 (empty) or 8 (full) valence electrons & is STABLE Na + 1 valence electron- -unstable Electron dot diagam ¨ Cl: ¨ 7 valence electrons--- unstable or

6. (A) Metals lose their outer electrons to acquire a noble gas structure and become positive ions. (B) Nonmetals gain electrons to acquire an outer noble gas structure and become negative ions. Metal Non-Metal Flourine (F) F- Lithium (Li) Li+ Li+ and F- will form an ionic bond Li + + F -  LiF.

7. :Ö :: Ö: Each atom has 8 valence electrons and is STABLE Electron dot diagram showing how valence electrons are shared (with circles) Note that all atoms in drawing are non-metals III. Types of Chemical Bonds –COVALENT BONDS:When atoms share electrons a covalent bond is formed (when 2 non-metals bond). :Ö: 6 valence electrons--- unstable :Ö: + 6 valence electrons--unstable Electron dot diagam or

8. IV. Chemical Formulas Atoms form elements, compounds., and molecules. Chemical formulas show the make-up of elements, compounds, and molecules. Chemical formulas follow these rules: Electron dots are not included ( written as NaCl). Subscripts (example: H 2 ) after symbols indicate the number of that atom present (NaHCO 3 has 3 oxygens) When no subscript is present, that indicates that one atom is present. If the subscript follows a parenthesis, all atoms within the parenthesis are present in that amount (Mg(OH) 2 has 2 oxygens). A coefficient in front of the element, compound, or molecule (example: 3 OH) indicates there are multiple molecules present (4CaCO 3 has 12 oxygens). ¨ Na:Cl: ¨