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Unit 3 Review

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. 39 K +1. Mass. Charge.

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Unit 3 Review

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

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

  3. 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

  4. SKIP! 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. Groups = Columns = Valence Electrons

  5. Ions • Atoms that have either lost or gained electrons are called ions. • Ions that GAINelectrons have a NEGATIVE charge and are called anions. • Ions that LOSEelectrons have a POSITIVECharge and are called cations. Has a “t” that looks like a “+” sign!

  6. 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.

  7. Oxidation vs Reduction • Elements in columns 1-13 tend to undergo Oxidation (lose electrons) and form Positiveions. These are metal elements • Elements in columns 15-17 tend to undergo Reduction (gain electrons) and form Negativeions. These are non-metal elements Oxidation Reduction Is Is Loss Gain

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

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

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

  11. Types of Chemical Reactions + • Synthesis • Decomposition • Single Replacement • Double Replacement • Dissociation • Combustion + + + + + + charge - charge + Hydrocarbon + O2 CO2 + H2O

  12. 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

  13. 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

  14. molar mass Calculating molar mass 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

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

  16. 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 = 24.3 MgF2 mass = 24.3 + 19 + 19 = 62.3 So... 24.3 x 100 = 39 % 62.3

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

  18. 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

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

  20. 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.

  21. Click here to get more practice with Balancing Reactions + + SC + T  CT2 + S 2 The coefficients balance out the equation THIS IS NOT BALANCED! Coefficient indicates how many Subscript indicates bonding

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