Catalyst 1 Draw the Lewis Structure for BCl

Catalyst 1. Draw the Lewis Structure for BCl 3. 2. Draw the Lewis Structure for HCN. 3. Draw the Lewis Structure for PCl 5

Formal Charges • Many compounds have more than 1 possible Lewis structure. • Formal charges tells us the “right” Lewis structure. • Formal Charge – The charge an element would have if all electrons were shared equally. • The “best” structure has: 1. Atoms that have formal charges closest to 0 2. Highest negative charge on the most electronegative atom

Calculating Formal Charges • To calculate formal charge:

Class Example • Draw NCS–, calculate its formal charge and pick the “best” Lewis structure.

Table Talk • Draw the Lewis structure for PF 3 and label the formal charge of all atoms

Meet the Bicarbonate Ion…

HCO 3 – + H+ H 2 CO 3 CO 2 + H 2 O

Justify – TPS • Which structure of bicarbonate drawn on the board is “right” according to our rules of formal charges?

Lecture 2. 2 – Resonance Structures and Polar Covalent Compounds

Today’s Learning Target • LT 2. 4 – I can discuss the reason for the formation of resonance Lewis Structures and I can draw resonance structures for a variety of covalent compounds.

Resonance Structures • Oftentimes, there is more than one “correct” way to draw a Lewis structure. • This occurs because there are multiple drawings with the same formal charges.

Class Example • Draw all the allowed structures for O 3

Resonance Structures • For O 3, both structures are equally valid • Resonance Structures – Molecules that require multiple Lewis Structures to describe the distribution of electrons. • Both structures are present in equal amounts

Resonance Structure for Ozone

Table Talk • Draw all the correct structures for SO 3 -

Table Talk • Draw all correct resonance structures for HCO 2 -

Coach and Correct

Question 1 • Draw all resonance structures for the nitrate ion

Question 2 • Draw all resonance structures for the phosphate ion

Question 3 • Draw all resonance structures for S 2 CO-2

Question 4 • Draw all resonance structures for SCN -

Question 5 • Draw all resonance structures for CHO 2 -

Amazing Bending Water!

Justify – TPS • What caused the water to bend?

Today’s Learning Targets • LT 2. 5 – I can characterize ionic and covalent compounds utilizing the idea of electronegativity. Furthermore, I can discuss how electronegativity differences lead to the formation of polar covalent bonds

Electronegativity • Electronegativity – The ability of an atom in a molecule to attraction electrons to itself. • Increases as you move across a period • Adding more protons, but not adding more energy levels • Decreases as you go down a group • Adding more energy levels makes it harder for the nucleus to attract new electrons

Covalent Bond Polarity • Oftentimes, when atoms are in a covalent bond, electrons are not shared equally. • Nonpolar Covalent Bond – Electrons shared equally between the atoms • Polar Covalent Bond – Electrons shared unequally due to difference in electronegativity • Electrons in a covalent bond reside closest to the atom that is most electronegative

H F Because fluorine is drastically more electronegative, it holds electrons closer to itself when in a covalent bond with hydrogen.

H F Hydrogen is given a partial positive charge and fluorine is given a partial negative charge

Table Talk • Label the location of the partial positive and partial negative charges in water.

Dipole Moments • The creation of a polar compound leads to the concentration of charge at the poles of the element. • Indicate dipole moment with an arrow that starts at positive and goes to the negative end H F

Bonding is a Spectrum • The difference in electronegativity tells us the type of bond that a compound has. • Don’t worry about exact values, you can do this qualitatively

Around the World • Determine if the compounds around the room are ionic, polar covalent, or non-polar covalent

Exit Ticket 1. Draw all the resonance structures for NO 3–. Label the formal charges on all atoms. 2. Draw the Lewis structure for HCl. Draw the dipole moment on the compound

Rate Yourself • Based on the exit ticket and your current level of understanding, rate yourself 1 – 4 on LT 2. 1, 2. 2, 2. 3, 2. 4, and 2. 5

Closing Time • You should read section 8. 1 – 8. 7 for Thursday/Friday • Answer questions 8. 1, 8. 4, 8. 22, 8. 24, 8. 39, 8. 41, 8. 47, 8. 48, 8. 52, 8. 63, and 8. 64 for Thursday/Friday