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Announcements

Important announcements for the chemistry class, including joining the clicker, graded work availability, discussion quiz, and upcoming exam. Lesson review on colligative properties, acid-base reactions, and chemical bonding.

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Announcements

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  1. Announcements • To join clicker to class today: • Turn on the Clicker (the red LED comes on). • Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). • If you are in one of Dr. Plude's lab sections and did not get graded work back, it is available in folders outside his office. • Discussion quiz today on Sections 5.1-5.4, 5.6 & 5.7. • Will be starting Chapter 6 today. • Exam on Chapters 5 and 6 one week from Wednesday.

  2. Review • Molar mass from colligative properties. • Solve Π= iMRT, ∆Tb = imKb, ∆Tf = imKf for M or m. • Use to convert mass of solute in solution to mass per mole. • Acid base RXNs. • H+(aq) + OH- (aq) –> H2O • Acids = compounds that release H+ in water. • Bases = compounds that release OH- in water. • Precipitation RXNs • vocabulary: unsaturated, saturated, supersaturated.

  3. Chapter 6 – Chemical Bonds • Valence Electrons • Review of Ionic Bonding • Covalent Bonding • octet rule – electronegativity • electron affinity – bond polarity • Continuum between ionic and covalent bonds (classification using bond-type triangle) • More complex examples: • Ozone and CFCs – resonance • formal charge – octet exceptions • bond order – bond length • F. Molecular Orbital Theory

  4. Systematic Lewis Structures • Octet rule: all main group (s and p block) elements except B (6) and H (2) will share electrons to get 8 valence electrons. • Count the total number of valence electrons on all atoms. • Next draw single bonds from each of the outer atoms to the central atom. Subtract two electrons from the total number of electrons for each bond you have made = # electrons you have left to use elsewhere. • Put electrons on the outer atoms to give each atom a total of eight (an octet). (H) hydrogen only needs 2 electrons. (B) boron usually only 6 electrons. Keep track of how many electrons you are using. If you run out of electrons before filling the outer atoms' octets, stop. • Any electrons that were not used up in step 3 should be put on the central atom. You should now have no unused valence electrons. • If any atoms do not have octets, make multiple bonds (double and triple) by sharing electron pairs from atoms that do have octets. • Look for resonance structures. If you have made multiple bonds or have odd electron species where all the atoms cannot have octets, there may be more than one way to arrange the multiple bonds or place the odd electron. If so, the molecule is better modeled as an average of all the possible structures.

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