Unit 3 Review This PowerPoint follows along with the Unit 3 Review Worksheet

Protons Neutrons Electrons Atomic number = # Protons Atomic number = # Electrons – Unless there is a charge Atomic mass - # protons = # neutrons Reminder: Oxidation State is the same thing as Charge 39 K +1 ChargeMass

Principle Energy Levels The electron clouds are found at specific distances from the nucleus called Principle Energy Levels Elements in the same row of the periodic table have the same number of occupied energy levels Periods = Rows = Principle Energy Levels

Valence Electrons The electrons that occupy the highest energy level (or the outer shell) are called Valence Electrons Elements in the same column of the Periodic Table have the same number of valence electrons and have similar chemical properties. SKIP! Groups = Columns = Valence Electrons

Ions ions Atoms that have either lost or gained electrons are called ions. Ions that GAIN electrons have a NEGATIVE charge and are called anions. Ions that LOSE electrons have a POSITIVE Charge and are called cations. Has a “t” that looks like a “+” sign!

Gain or Lose ? Atoms will gain or lose electron in order to obtain a full outter shell. This means they may lose electrons to empty the last shell, or gain electrons to fill the last shell (with 8 electrons, except for Hydrogen and Helium) – Lithium only has 1 valence electron so it would rather lose 1 than gain 7. This means it will have a charge of +1. – Fluorine has 7 valence electrons so it would rather gain 1 than lose 7. This means that it will have a charge of -1.

Oxidation vs Reduction Elements in columns 1-13 tend to undergo Oxidation (lose electrons) and form Positive ions. These are metal elements Elements in columns tend to undergo Reduction (gain electrons) and form Negative ions. These are non-metal elements OxidationReduction IsIsIsIs LossGain

Lithium Loses an Electron Li  Li e- Electron is being lost resulting in a positive charge Li Li +1

Fluorine gains an electron F + 1 e-  F -1 Fluorine gains an electrons resulting in a negative charge F -1 F

Lithium Fluoride When lithium loses and electron, it will give it to fluorine resulting in an ionic bond

Types of Chemical Reactions Synthesis Decomposition Single Replacement Double Replacement Dissociation Combustion charge - charge Hydrocarbon + O 2  CO 2 + H 2 O

Criss Cross Method Mg +2 + P -3  Mg 3 P 2 3(+2) + 2(-3) = 0 Take the absolute value of the charges and switch the value with the other element to obtain the subscript value

Naming Compounds Positive Metal Name + Negative Non-Metal Name (change ending to “ide”) Example: Na 2 O sodium oxide Note that the subscripts do NOT have any affect on the name

Moles… H 3 PO 4 contains 98 grams per 1 moles If you have a container with 343 grams of H 3 PO 4, how many moles does it contain? H = 1 gram per mole x 3 = 3 grams P = 31 grams per mole x 1 = 31 grams O = 16 grams per mole x 4 = 64 grams Total = 98 grams Calculating molar mass molar mass

343 grams = 3.5 moles Dimensional Analysis Ratio / Cross Multiplying 98 grams = 1 mole 343 grams = X moles 1 (343)98 X = 1(343) = 98X X = 3.5 moles 1 mole 98 grams ( ) molar mass

Calculating percent by mass… The percent by mass of an element in a compound can be determined: % by mass of element = total mass of element in compound X 100 total mass of the compound Example: Calculate the percent composition of magnesium in MgF 2. Mg mass = 24.3 MgF 2 mass = = 62.3 So x 100 = 39 % 62.3

When a bond is broken energy is required. When a bond is made energy is released. Reactants  Products ENDOTHERMIC EXOTHERMIC

Particles speed up when heat is added, this process is considered endothermic because heat is absorbed. Particles slow down when heat is removed, this process is considered exothermic because heat is lost HEAT

Temp. Melting  H + endothermic Boiling  H + endothermic Freezing  H – exothermic Condensing  H – exothermic Time heat added

Balancing Reactions Because of the law of conservation of mass, reactions must have the same amount of atoms in their reactants as they do in their products. The atoms can be rearranged into different compounds, but there must be the same amount.

+ + SC + T  CT 2 + S THIS IS NOT BALANCED! 2 The coefficients balance out the equation Subscript indicates bondingCoefficient indicates how many Click here to get more practice with Balancing Reactions