1. Unit 5: Chemical Formulas and Bonding Chapters 7 and 8

2. Unit # 5: Chemical Composition I. “Intra-Chemical” Bonding A. Definition: atoms (elements) held together by an attractive force B. Types (3) 1. Metallic: atoms of a metal “share” the valence electrons because they move from one element to another

3. 2. Ionic (strongest) a. Definition: electrons are transferred from one element to another (opposite charges is attractive force) b. Called: “salts” c. Atom that donates electron:(+)cation Atom that accepts electron:(-) anion Atom that accepts electron:(-) anion d. Oxidation State (number): Charge of an ion

4. e. Lewis Dot Formulas – used to show outer shell electron transfer - Octet Rule: every element wants 8 electrons in its outer shell 1. potassium + chlorine  potassium chloride (show on board) 2. magnesium + fluorine  magnesium fluoride (show on board) f. Types of Ions 1. Monatomic Cation: cation with one element

5. 2. Monatomic Anion: anion with one element (ends with –ide) 3. Polyatomic Ions: AmmoniumNitrate ChromateSulfate AcetateHydroxide ChlorateCarbonate PhosphatePermanganate

6. g. Writing Chemical Formulas 1. Composition 2. Number of elements 3. Writing chemical formulas (from the name) a) Recognize the (+) and (-) ions b) Write the symbols of the elements with their charge * Note- a Roman numeral will tell you what the charge is on the cation if there is more than one possibility

7. c) Adjust the number of each ion (with subscripts) as needed so the positive charge is equal and opposite the negative charge. Note – if the ions are polyatomic and there is more than one, the ion is enclosed with parentheses with a subscript on the outside. Note – if the ions are polyatomic and there is more than one, the ion is enclosed with parentheses with a subscript on the outside. Examples: Examples: Sodium Chloride(on board) Calcium Sulfate(on board) Barium Phosphate(on board)

8. h. Naming Compounds 1. Consists of two words: a) Name the cation b) Name the anion c) If the cation has more than one possible charge, a Roman Numeral is used to show the charge. Ex: FeCl3Fe  Iron (III) Chloride FeCl2Fe  Iron (II) Chloride FeCl2Fe  Iron (II) Chloride +3 +2

9. Ex: NH4Cl Cu2SO4NaC2H3O2 3. Covalent (weaker) a. Definition: valence electrons are shared between two elements Ex: F2 (show electron dot diagrams for bonding) (show electron dot diagrams for bonding)

10. b. Types 1. Polar Covalent (stronger): unequal sharing of electrons (one pulls more than the other – the more electronegative element) 2. Non-Polar Covalent (weakest): equal sharing of electrons c. Lewis Structures 1. examples (hydrogen and HCl)

11. 2. The number of covalent bonds formed by an atom equals the number of unpaired electrons in the Lewis Dot Formula. 3. Examples a) water b) ammonia c) methane d. Multiple Bonds 1. Double bonds: two pairs of electrons are shared (Ex: oxygen gas - draw it)

12. 2. Triple Bonds: three pairs of electrons areshared (Ex: nitrogen gas- draw it) e. Hybridization: combining of two or more orbitals of nearly the same energy into new orbitals of equal energy Ex. 1) C 1s22s22p2sp3 hybrid __ __ __ __ -----> __ __ __ __ 2s 2p acquires energy 2s2p 2) B 1s22s22p1sp2 hybrid __ __ __ __ -----> __ __ __ __ 2s 2p acquires energy 2s2p f. Molecules with more than one element (polar vs. non-polar) 1) Depends On: - electronegativity difference (2 elements) - Non-bonded electron pairs (2+ elements) - Non-bonded electron pairs (2+ elements) - Structure (symmetry) (2+ elements) - Structure (symmetry) (2+ elements)

13. g. Shapes of Molecules (VSPER handout) h. Naming/Writing Formulas for Covalent Compounds 1. Binary covalent compounds (2 elements) 2. Formulas with two non-metals 3. Rules a) First word: - prefix indicating the # of atoms for the first element (if there is more than one) - name of first element b) Second word: - prefix for the number of atoms of the second element - name of second element

14. II. “Inter-Chemical” Bonding A. Definition: whole “salts” or “molecules” attract and bond with one another. B. Types 1. Hydrogen Bonding (medium strength): H bonded to N, O, or F 2. “VanderWaals” Forces a. Dispersion (weakest): if not H-bonding or dipole-dipole, it must be dispersion b. Dipole-Dipole (strongest): between polar molecules