Happy Chemistry Day! Please take out: Quiz Today! (again ) Both Worksheets that were homework New Homework (purple sheet in the back) 2 white half sheets (tape in Notes section) Your homework sheet Your lab notebook open to your warm-up section Quiz Today! (again )

Reminders… Naming Unit TEST is next week: Blue 11/8 and Gold 11/9 Ionic, Covalent, Acid Naming quiz retakes next class (I’ll take the higher of your two scores) Last day for Nuclear Test corrections and retake is 11/9 Nuclear Unit extra credit is due 11/9 (see my Swift site under “homework and worksheets”)

Warm-up PI3 H2SO3 H2S C2Br2 S2F6 Phosphorus trifluoride Name the molecules/acid: Write the formula for the molecule/acid: PI3 H2SO3 H2S C2Br2 S2F6 Phosphorus trifluoride Phosphoric Acid Hydronitric Acid Nitric Acid Tricarbon monochloride Phosphorus triiodide PF3 Sulfurous Acid H3PO4 Hydrosulfuric Acid H3N Dicarbon dibromide HNO3 Disulfur hexafluoride C3Cl

HW Review Log on your homework sheet Practice with your partner

Quiz! Try your best! Please flip it over once you are finished! Draw your best “Thanksgiving Turkey” on the back.

Learning targets!!!!! I can draw the Lewis Dot structure of a nucleus based on the total number of valence electrons. Predict the VsPER shape of a molecule from its Lewis structure.

What do molecules look like? Why? Molecular Geometry What do molecules look like? Why?

Lewis Structures Drawings that show how electrons in the outer shell are arranged (valence) A line indicates two atoms bonding and sharing 2 electrons All elements want 8 electrons in their outer shell Exceptions: Hydrogen wants 2; Boron wants 6

Steps of Drawing Lewis structures Determine the total number of valence electrons available for each molecule/ion. Add up the valence electrons for each atom in the molecule. In the case of ions, add one electron for each negative charge or subtract one electron for each positive charge. Draw a “skeleton” structure connecting all of the atoms to the central atom with single bonds. If there is a single atom of one element in a compound, show it as the central atom with other atoms joined to it. Hydrogen is never a central atom. If there are two single atoms in a compound, the least electronegative atom should be the central atom. (In a tie, pick Carbon). Give each atom enough unshared pairs of electrons to fulfill the octet (Hydrogen follows the duet rule – it only wants 2 electrons in its outer orbital. The other exception is Boron, which only wants 6 electrons.) Count up the number of electrons used in your Lewis Dot structure. If your drawing’s total number of valence electrons are greater than the number of valence electrons available, multiple bonds (double or triple) may be needed. Remember that bonding electrons are “shared by both atoms” in the bond while unshared electrons are “owned” to only one atom. (Only if you need multiple bonds) Re-draw the skeleton using a double or triple bond if needed. Repeat steps 3 & 4 until your drawing’s total number of electrons matches the total number of valence electrons available. 6. Isomers= multiple arrangements of same molecule

Let’s go through the steps! I’ll do the first two, you do the second two: 1. H2O 2. PH3         3. CCl4 4. N2

Answers! H2O PH3         CCl4 N2

Answers! H2O PH3         CCl4 N2

Summary of Lewis Dots Lewis Structures show us the 2D arrangement of atoms in a molecule or compound using valence e- Valence e- can be shared or lone pairs Can have multiple versions (resonance structures) But how do they look in 3D?

5 Geometric Structures To Know

Why are molecules these shapes? Valence Shell Electron Pair Repulsion (VSEPR Model) Structure minimizes repulsions between electron pairs Keep lone pairs as far from the bonded pairs as possible! You need to know the following structures: Linear Bent Trigonal Planar Trigonal Pyramidal Tetrahedral

How Do I Know What Shape it is? Draw the correct Lewis Dot structure (see above). Shape is determined by the central atom. If there are only TWO elements – no “central” atom: Shape is linear. If central atom is connected to TWO elements: If central atom has one or two unshared pair(s) of electrons: Shape is bent. If central atom has zero unshared pairs of electrons: Shape is linear. If central atom is connected to THREE elements: If central atom has one unshared pair of electrons: Shape is trigonal pyramidal. If central atom has zero unshared pairs of electrons: Shape is trigonal planar. If central atom is connected to FOUR elements: Shape is tetrahedral.

Examples: linear vs. bent

Examples: Trigonal Planar And Tetrahedral

Example: Trigonal Pyramidal

There are others …. Trigonal Bipyramidal Square Pyramidal Yellow sphere is a pair of unbonded electrons

Square Planar Octahedral http://www.infosources.org/what_is/VSEPR_theory.html

Due Next Class Do the “Drawing Lewis Structures” worksheet For molecular geometry, first predict based on your Lewis Dot Structure Then double check yourself with the PheT link on my swift site!

Exit Task Thought question… Elements in periods 3 and below can have more than four bonds (an expanded octet). For example, Phosphorus can have up to 5 bonds, and Sulfur can have up to 6 bonds. Why do you think this is? The “d” shell!

Steps of Drawing Lewis structures Determine the total number of valence electrons available for each molecule/ion. Add up the valence electrons for each atom in the molecule. In the case of ions, add one electron for each negative charge or subtract one electron for each positive charge. Draw a “skeleton” structure connecting all of the atoms to the central atom with single bonds. If there is a single atom of one element in a compound, show it as the central atom with other atoms joined to it. Hydrogen is never a central atom. If there are two single atoms in a compound, the least electronegative atom should be the central atom. (In a tie, pick Carbon). Give each atom enough unshared pairs of electrons to fulfill the octet (Hydrogen follows the duet rule – it only wants 2 electrons in its outer orbital. The other exception is Boron, which only wants 6 electrons.) Count up the number of electrons used in your Lewis Dot structure. If your drawing’s total number of valence electrons are greater than the number of valence electrons available, multiple bonds (double or triple) may be needed. Remember that bonding electrons are “shared by both atoms” in the bond while unshared electrons are “owned” to only one atom. (Only if you need multiple bonds) Re-draw the skeleton using a double or triple bond if needed. Repeat steps 3 & 4 until your drawing’s total number of electrons matches the total number of valence electrons available. Isomers = multiple arrangements of same molecule

How Do I Know What Shape it is? Draw the correct Lewis Dot structure . Shape is determined by the central atom. If there are only TWO elements – no “central” atom: Shape is linear. If central atom is connected to TWO elements: If central atom has one or two unshared pair(s) of electrons: Shape is bent. If central atom has zero unshared pairs of electrons: Shape is linear. If central atom is connected to THREE elements: If central atom has one unshared pair of electrons: Shape is trigonal pyramidal. If central atom has zero unshared pairs of electrons: Shape is trigonal planar. If central atom is connected to FOUR elements: Shape is tetrahedral.