unit 3 review
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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
39K+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
• Atoms that have either lost or gained electrons are called ionsions.
• 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 15-17 tend to undergo Reduction (gain electrons) and form Negative ions. These are non-metal elements
Oxidation ReductionIs IsLoss Gain
Lithium Loses an Electron
Li Li+1 + 1 e-
Electron is being lost Electron is being lost resulting in a positive chargeresulting in a positive charge
LiLi LiLi+1+1
Fluorine gains an electron
F + 1 e- F-1
Fluorine gains an electrons Fluorine gains an electrons resulting in a negative chargeresulting in a negative charge
FF-1-1FF
Lithium Fluoride
When lithium loses When lithium loses and electron, it will and electron, it will give it to fluorine give it to fluorine
resulting in an ionic resulting in an ionic bondbond
Types of Chemical Reactions
• Synthesis
• Decomposition
• Single Replacement• Double Replacement
• Dissociation
• Combustion
+
++ +
+ +
++ charge
- charge
Hydrocarbon + O2 CO2 + H2O
Criss Cross Method
• Mg+2 + P-3
Mg3P2
• 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:• Na2O
• sodium oxide
Note that the subscripts do NOT have any affect on
the name
Moles…
• H3PO4 contains 98 grams per 1 moles If you have a container with 343 grams of H3PO4 , 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 98 98
X = 3.5 moles
1 mole98 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 MgF2.
Mg mass = 24.3MgF2 mass = 24.3 + 19 + 19 = 62.3
So... 24.3 x 100 = 39 % 62.3
• When a bond is broken energy is required.
• When a bond is made energy is released.
Reactants ProductsENDOTHERMIC
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
HEAT
Tem
p.
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 CT2 + 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
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