Lesson 4: Electronegativity and Hybridization

*CRB* What will the orbital geometry be for a carbon that is sp3 hybridized? (A) Octahedral (B) Trigonal bipyrmaidal (C) Bent (D) Tetrahedral

(D) Tetrahedral A carbon that is sp3-hybridized will have tetrahedral orbital geometry.

*CRB* What will be the orbital geometry of a Carbon that is sp2-hybridized? (A) Octahedral (B) Bent (C) Linear (D) Trigonal Planar

(D) Trigonal Planar A carbon that is sp2-hybridized will have a trigonal planar orbital geometry.

Does CO2 have a dipole moment?

It has polar bonds but does not have a dipole moment, therefore the molecule itself is nonpolar. Two vectors have equal magnitude and opposite direction so they cancel each other out.

sp orbitals have what percent s character and what percent p character?

sp orbitals have 50 percent s character and 50 percent p character.

sp2 orbitals have what percent s character and what percent p character?

sp2 orbitals have 33 percent s character and 67 percent p character.

What is the steric number for methane?

tetrahedral arrangemet of electrons and tetrahedral arrangement of atoms

What is the equation for dipole moment (μ)?

μ = q d μ = Dipole Moment q = magnitude of Charge d = Distance

Cl- and H+ have partial charges of -4.76⋅10^-34 C and 4.76⋅10^-34 C, respectively. they are separated by a distance of 2.21⋅10^28 m. What is the dipole moment for HCl based on these numbers? (A) 1.05⋅10^-5 (B) 4.62⋅10^-6 (C) 3.98⋅10^-7 (D) 9.45⋅10^-8

(A) 1.05⋅10^-5 μ = q d μ = (4.76⋅10^-34 C)(2.21⋅10^28 m) μ = approx. 10⋅10^-6 (actual: 10.52⋅10^-6)

*CRB* Polarity can be used to stabilize Carbocations or Carbanions by donating or withdrawing electron density, respectively. Which of the following will be the most stable Carbocation? (A) CH3 (B) CH2N (C) CH2Br (D) CCl3

(A) CH3 To stabilize this carbocation, electron donating groups (read as Less Electronegative than Carbon) should be bound to Carbon. Nitrogen, Bromine and Chlorine are all more electronegative, so CH3 is the best answer.

Which intermolecular force is a result of attraction between the oppositely-charged ends of two polar molecules? (A) Dipole-dipole Interaction (B) Hydrogen Bonding (C) London Dispersion Forces (D) Covalent Bonding

(A) Dipole-dipole Interaction A Dipole-dipole Interaction is a result of attraction between the oppositely-charged ends of two polar molecules The intermolecular force depends on electronegative of atoms within the compound

The sp3 orbitals of Carbon join with the s orbitals of Hydrogen to make Methane (CH4), forming what type of bonds? (A) σ Bond (B) π Bond (C) α Bond (D) β Bond

(A) σ Bond The sp3 orbitals of Carbon join with the s orbitals of Hydrogen to make Methane (CH4), forming four σ Bonds. bond formed via head on overlap

*CRB* Based on the previous card, which of the following orbital geometries is most likely for a carbanion? (A) Bent (B) Tetrahedral (C) Linear (D) Trigonal Bipyramidal

(B) Tetrahedral A carbanion takes on a slightly-distorted tetrahedral orbital geometry. That slight distortion is due to increased repelling from a lone pair than from two electrons in a covalent bond. Note that the molecular geometry and orbital geometry will be different in this case.

*CRB* A carbocation would take on the same orbital geometry of which of the following hybridizations? (A) sp3 (B) sp2 (C) sp (D) None of the above

(B) sp2 A carbocation has an empty p-orbital, and the other three orbitals will adopt the trigonal planar form that sp2-carbons use to maximize the space between each orbital.

The sp2 orbitals will form _______ bonds while the p orbitals will form _______ bonds in making C2H4? (A) σ,σ (B) σ,π (C) π,σ (D) π,π

(B) σ,π The sp2 orbitals will form σ Bonds with Hydrogens' s orbitals while the p orbitals will form π Bonds with each other in making C2H4.

Cholesterol (https://pubchem.ncbi.nlm.nih.gov/image/imgsrv.fcgi?cid=5997&t=l) has an important biochemical role in our bodies. How many sp3 carbons does it contain? (A) 15 (B) 23 (C) 25 (D) 48

(C) 25 Cholesterol contains 25 sp3 hybridized carbons. Do not forget the two carbons from wedges and one from dashes! Only the two carbons in the double bond are not sp3 hybridized here

What is the steric number for XeF6 (periodic table: http://www.sbcs.qmul.ac.uk/iupac/AtWt/table.gif)? (A) 5 (B) 6 (C) 7 (D) 8

(C) 7 SN = σ + LP SN = 6 + 1 SN = 7

What will be the molecular geometry of a Carbon that is sp-hybridized? (A) Octahedral (B) Bent (C) Linear (D) Trigonal Planar

(C) Linear An sp-hybridized Carbon will have a linear molecular geometry.

Which intermolecular force is a result of polarization of electron clouds between non-polar molecules? (A) Dipole-dipole Interaction (B) Hydrogen Bonding (C) London Dispersion Forces (D) Covalent Bonding

(C) London Dispersion Forces London Dispersion Forces result from the polarization of electron clouds between non-polar molecules. Weakest intermolecular force

*CRB* Polar bonds can be used to stabilize Carbocations (carbon atom with positive charge) or Carbanions (carbon atom with negative charge) by donating or withdrawing electron density, respectively. Which of the following will be the most stable Carbanion? (A) CH3 (B) CH2N (C) CH2Br (D) CCl3

(D) CCl3 The most stable Carbanion will have electron-withdrawing groups to stabilize the negative charge.

*CRB* Another way to stabilize a carbocation or carbanion is by delocalizing the charge by having multiple resonance structures with the charge on different Carbons by moving double bonds. Which term properly describes this stabilizing property of multiple resonance structures? (A) Inducibility (B) Connectivity (C) Allylic (D) Conjugation

(D) Conjugation Conjugation allows for delocalized charges by allowing a pi bond to exist between different (more than 2) adjacent carbons.

Put the following bond types in order from weakest to strongest: I. Dipole-dipole Interaction II. Hydrogen Bonding III. London Dispersion Forces IV. Covalent Bonding (A) I < III < IV < II (B) I < III < II < IV (C) III < II < I < IV (D) III < I < II < IV

(D) III < I < II < IV In order from weakest to strongest: London Dispersion Forces < Dipole-dipole Interaction < Hydrogen Bonding < Covalent Bonding

In C2H2, are the following bonds made of sp orbitals or p orbitals? 1. σ bonds between Carbon and Hydrogen 2. σ bond between Carbon and Carbon 3. π bonds between Carbon and Carbon

1. σ bonds between Carbon and Hydrogen - sp orbitals 2. σ bond between Carbon and Carbon - sp orbitals 3. π bonds between Carbon and Carbon - p orbitals Sigma bond forms from direct overlap of orbitals

An sp3 orbital has what percent s character and what percent p character?

25 percent s character and 75 percent p character.

What is the steric number of BF3?

Boron has an empty p orbital which makes it able to accept an electron pair acting as lewis acid Boron is sp2 hybridized

Compare the polarity of CCl4 and CHCl3. Why is the polarity the same/different?

CCl4 is non-polar due to its symetrical structure. CHCl3 is polar due to its non-symetrical structure. Geometry is tetrahedral around those carbons

*CRB* True or false? Because both carbocations and carbanions have an unhybridized p-orbital, they will have the same orbital geometry.

False. Carbocations have a vacant p-orbital, so they can adopt a trigonal planar orbital geometry. Carbanions have a lone pair of electrons there that will repel the other three orbitals, preventing a trigonal planar orbital geometry.

*CRB* Hey, CCl3 is a non-polar molecule! I thought you said that polarity is what will stabilize the carbanion? Please explain how this works.

For this stabilizing inductive effect to occur, there must be Polar Bonds, not necessarily a polar molecule! All that matters is that the carbanion has less electron density, not where the electron density moves to or if it is evenly distributed amongst the other atoms in the molecule.

Does water have a dipole moment?

Individual dipoles from polar bonds add to give a net dipole pointing upwards SO water is polar

What is the difference between intermolecular forces and intramolecular forces?

Intermolecular Forces are between two difference molecules. Intramolecular Forces are between the same molecule.

Describe Hydrogen bonding

It is a stronger version of a dipole dipole interaction where hydrogen binds to a very electronegative atom. The hydrogen itself must initially be bonded to another electronegative atom that pulls electron density away from it. Fluorine, oxygen, and nitrogen are the typical atoms involved in H bonding with H

What is the purpose of the Steric Number?

It tells you how many hybridized orbitals you have in the central atom.

What is the steric number of a carbon in c2h4?

Need 3 hybrid orbitals. So a steric number of 3 is sp2 hybridization

The Carbons of C2H4 need 3 hybrid orbitals (such as sp, sp2 or sp3) each, yet they each have only 2 orbitals with a single electron (and one orbital with a lone pair of electrons). What will they do?

One of the 2s orbital electrons jumps up to fill the empty 2p orbital. Two of the three 2p orbitals then hybridize with the single 2s orbital, forming three sp2 orbitals and leaving one remaining p orbital. There is a single electron in each of these 4 described orbitals.

The Carbons of C2H2 only need 2 hybrid orbitals each, and they have 2 orbitals with lone pairs of electrons (and one orbital with a lone pair of electrons). What will they do?

One of the 2s orbital electrons jumps up to one of the 2p orbitals. One of the three 2p orbitals then hybridize with the single 2s orbital, forming two sp orbitals and two p orbitals with a lone electron in each.

If Carbon only has two 2p electrons, how does it form four bonds to make Methane (CH4)?

One of the 2s orbital electrons jumps up to one of the 2p orbitals. The three 2p orbitals then hybridize with the single 2s orbital, forming four sp3 orbitals with a lone electron in each. All sp3 orbitals are same energy Since we are doing this using one s orbital and 3 p orbitals, we call this sp3 hybridization

What equation is used to determine the steric number in terms of the number of σ Bonds in a compound?

SN = σ + LP SN = Steric Number σ = # of Sigma Bonds LP = # of Lone Pairs

Draw the electron configuration (electron energy levels diagram) for Carbon?

See image.

How does boiling pint relate to the strength of the intermolecular force?

The stronger the intermolecular force, the higher the boiling point

True or False? σ Bonds can freely rotate while π Bonds cannot.

True. σ Bonds can freely rotate while π Bonds cannot.