REVIEW LECTURE

Drawing Lewis Dot Diagrams ● First you need to identify the number of valence electrons ● Find the V.E. from writing out the shorthand configuration ● Or based upon the group that it’s in find the number of V.E. from that. ● Second, place the elements valence electrons around the chemical symbol

Bonding Atoms ● Why do atoms bond? - each atom wants a full outermost energy level - gain, lose, and share valence electrons to achieve the duet or octet rule aka: “being happy” - gives each atom an electron configuration similar to that of a noble gas ex. Group 18: He, Ne, Ar

Chemical Bonds ● Chemical Bonds - attractive force that holds atoms or ions together - 3 types ionic, covalent, metallic - determines the structure of compound - structure affects properties - melting/boiling pts, conductivity etc.

Chemical Structure/Models ● Chemical Structure/Molecular Models - arrangement of bonded atoms or ions - bond length: the average distance between the nuclei of two bonded atoms - bond angles: the angle formed by two bonds to the same atom

Ionic Bonds / Ionic Compounds ● Definition - bond formed by the attraction between oppositely charged ions cation: positive: lost e-’s anion: negative: gained e-’s - oppositely charged ions attract each other and form an ionic bond ex. Na + + Cl - = NaCl - electrons are transferred from one atom to another - negative ions attract more positive ions, and soon a network is formed

Properties of Ionic Compounds ● Structure affects properties - strong attractions between ions: strong bonds - high melting/boiling pt - shatter when struck (think of it as one unit) - conductivity solid: ions are so close together, fixed positions, (can’t move) NO conductivity liquid: ions are freely moving due to a broken lattice structure Good conductivity

How many Atoms? AND

How many Atoms?

Covalent Bonds ● Definition - chemical bond in which two atoms share a pair of valence electrons - can be a single, double, or triple bond single, 2e-’s (-); double, 4e-’s (=); triple, 6e-’s( ) - always formed between nonmetals - mostly low melting/boiling points ● 2 types of bonds - polar - non polar

Covalent Bond Cont. ● Non Polar - bonded atoms that share e - ’s equally - same atoms bonded ex. Cl – Cl: Cl 2 ● Polar - bonded atoms that do not share e - ’s equally - different atoms bonded H ex. H – N – H: NH 3

Predicting Bond Type

Types of Reactions 1.Synthesis reactions 2.Decomposition reactions 3.Single displacement reactions 4.Double displacement reactions 5.Combustion reactions You need to be able to identify each type.

1. Synthesis Example C + O 2 OO C + → OO C General: A + B → AB

2. Decomposition Example: NaCl General: AB → A + B → Cl Na Cl + Na

3. Single Displacement Example: Zn + CuCl 2 → Zn Cl Cu + General: AB + C → AC + B Cl Zn Cu +

4. Double displacement Example: MgO + CaS General:AB + CD → AD + CB S O → Mg Ca + O S Mg Ca +

Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s) → AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq) → KNO 3(aq) + BaSO 4(s) 2

5. Combustion Reactions Combustion reactions - a hydrocarbon reacts with oxygen gas. This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) Fuel (hydrocarbon) 2) Oxygen 3) Something to ignite the reaction (spark)

Combustion Reactions In general: C x H y + O 2 → CO 2 + H 2 O Products are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by-products like carbon monoxide) Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C 8 H 18 )

Mixed Practice State the type & predict the products. 1.BaCl 2 + H 2 SO 4 → 2.C 6 H 12 + O 2 → 3.Zn + CuSO 4 → 4.Cs + Br 2 → 5.FeCO 3 →

TIPS TO BALANCE RXNS

RULES TO BALANCING REACTIONS Find correct formulas for all the reactants and products. Write skeleton eq by placing the reactants on the left and products on the right. Find the number of atoms of each element in reactants and products. Polyatomic ions are a single unit if it appears on both side of rxn unchanged Write them in a table below equation. Balance elements one at a time. Check each atom or polyatomic ion to be sure they are equal Make sure coefficients are in the lowest possible ratio

BALANCE THE FOLLOWING Iron metal and chlorine gas react to form solid iron chloride Aluminum Carbonate decomposes to form aluminum oxide and carbon dioxide Magnesium reacts with aqueous silver nitrate to form silver and aqueous magnesium nitrate.

Fe+Cl 2 FeCl 3 Al 2 (CO 3 ) 3 Al 2 O 3 + CO 2 Mg + AgNO 3 Ag + Mg(NO 3 ) 2

2Fe+3Cl 2 2FeCl 3 Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 Mg + 2AgNO 3 2Ag + Mg(NO 3 ) 2

SO 2 + O 2 SO 3 Fe 2 O 3 + H 2 Fe + H 2 O P + O 2 P 4 O 10 Al + N 2 AlN

2SO 2 + O 2 2SO 3 Fe 2 O 3 + 3H 2 2Fe + 3H 2 O 4P + 5O 2 P 4 O 10 2Al + N 2 2AlN