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Chemical Interactions Review Notes Valence electron 1) Electron Movement based on what we did with Happy Atoms - Look at oxidation number - count how many it takes to be a noble gas - look at group/family number Ex. Na 11 p+ 11 e- N a Nucleus protons & Neutrons Bohr Diagram - shows all e- Lewis Dot Structure - shows on valence e- for bonding 2) Bonding Ion - atom or group of atoms with a charge (lose or gain valence e-) Ionic Bond - attractions between two oppositely charged atoms (includes metals and nonmetals, polyatomic ions) Ex. Na+1Cl-1 metal and a nonmetal Loses 1egains 1eOverall is neutral (charges cancel) Covalent Bond - atoms share electrons (nonmetal and nonmetal); can be polar (the share unequally) or nonpolar (share electrons equally) F2 F H2O F CO2 - O H O C O + H + Chemical Interactions Review Notes 8th Grade Science 1 3) Formulas and Equations Cr = chemical symbol representing an atom H2SO4 = chemical formula that tells the part of a substance (subscript numbers tell the # of each atom one is understood) Chemical equation tells what happens in a reaction 6CO2 + 6H2O → C6H12O6 + 6O2 Coefficient numbers tell how many molecules there are (multiplied) Reactants Products 4) Naming - words to symbols 1. Find symbols 2. Find charge (oxidation #) if metal or polyatomic ions are used; nonmetals use prefixes 3. Criss-cross (add subscripts unto charges balance) Ex. Magnesium+2 Chloride-1 ClMgCl2 Cl- Calcium+2 nitrate-1 Ca(NO3)2 5) Balancing equations - law of conservation of mass MgCl2 + 2 NaOH ----> Mg(OH)2 + 2 NaCl Double replacement Polyatomic 1. Count atoms 2. Find odd numbers or large numbers and fix first (leave oxygens and hydrogens until end) 3. Use coeffcients to indicate additionalmolecules 6) Types of Reactions Decomposition - break down compound 2 KCl ----> 2 K + Cl2 Synthesis - put atoms or molecules together 2 H2 + O2 --- > 2H2O Single Replacement - only one atom is replaced Mg + 2 ZnCl ---> MgCl2 + 2 Zn Double Replacement - swap partners MgCl2 + 2 NaOH ----> Mg(OH)2 + 2 NaCl Activation energy - gets reaction started Endothermic - absorbs energy - cool Exothermic - releases energy - hot KEY QUESTIONS - How do you know a chemical reaction occurs? - What happens between atoms and their electrons during a reaction? Chemical Interactions Review Notes 8th Grade Science 2 7) Acids/Bases Acids in water ----> H+ Bases in water ---> OHNeutralization - acid and base (double replacement) HCl H+ Cl- + NaOH Na+ OH- ----> H2O + ----> water NaCl salt (positive base ion with negative acid ion) pH - level of acidity based on concentration of H+ ions 0 __________________7________________14 More H+ neutral Less H+ Less OH More OH- Chemical Interactions Review Notes 8th Grade Science 3