100 likes | 106 Views
This study guide covers Lewis Structures, Bond Properties, and Covalent Bond Formation. Learn to draw structures, count bonding electrons, and identify exceptions to the Octet Rule. Practice examples like NF3 and CH2Cl2.
E N D
November 11, 2009 EXAM #3 Correction- Check OWL Chapter 8 Homework posted Today’s Topic: Lewis Structures (Sec. 8.2) Bond Properties (Sec. 8.3)
Why does a covalent bond form? • The valence electrons on two atoms are attracted to one another • The nuclei of two atoms are attracted to one another • The valence electrons on one atom are attracted to the nucleus of another atom • The repulsive forces between the protons in two nuclei and between the electrons in two atoms are strong
Last time… • Bonds form when the balance of forces favors bond formation • Valence electrons are those in the outermost shell (highest n-level) • Lewis structures are used to show the valence electrons • Elemental symbol = core (nucleus + inner electrons) • Lines = bonding electrons • Dots = electrons not involved in a bond
Rules for Drawing Lewis Structures • Write the skeletal structure • Add up the total # of valence electrons • Draw a bond between the central atom and each surrounding atom • Add lone pairs to the outer atoms to complete their octets • Add remaining electrons to central atom • If central atom does not have an octet, “borrow” electrons from other atoms (make double/triple bonds)- DO NOT ADD ELECTRONS (F and Cl do not form multiple bonds; C, N, O, P, and S do) • Sometimes you can’t complete an octet (B and Be)
How many total bonding electrons does an acetate ion have? • 7 • 8 • 10 • 12 • 13 • 14 • 15
Examples NF3 CH2Cl2 Try this one at home! CO2 O3
Draw the Lewis structure for SO3. How many lone pairs does it have? • 2 • 4 • 6 • 8 • 10
Exceptions to the Octet Rule • H (2) • Be (4) • B (6) • Large elements with available d orbital SF4 BF3 ClF5
Organic Structures • CH3CH3 • CH3CN • CHCCHCH2