px3 All bonding with all hybrid orbitals will occur on the larger lobe for each hybrid.

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Ronald Hines
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1 Reasons for ybridization 1. Allows atoms to have the correct number of unpaired electrons to make necessary number of bonds. 2. Best spatial orientation achieved least amount of electron repulsions 3. Stronger, more stable bonds as a result of overlapping orbitals with greater s character Sp 3 hybridization occurs when four groups of sigma bonds or lone pairs are present. When an atom hybridizes to sp 3, four sp 3 orbitals are formed and used for bonding or to hold lone pairs. Find the atoms with four groups : These atoms have a shape called tetrahedral, a bond angle of 109.5º. The sp 3 orbital is asymmetric in shape, with one lobe larger, which is good for overlapping with other orbitals, being formed from 25% s and 75% p orbital. Shape? px3 All bonding with all hybrid orbitals will occur on the larger lobe for each hybrid. You may also recall the shapes trigonal pyramid and bent, found when atoms have one or two lone pairs attached. This will tweak the bond angle a wee bit (107º or 104º). For the purpose of this course, please feel free to just call them tetrahedral and use 109.5º. Sp 2 hybridization occurs when three groups of sigma bonds or lone pairs are present. When an atom hybridizes to sp 2, then three sp 2 orbitals are formed, with one p orbital left over for forming pi bonds. Which atoms have three groups? This molecule contains a double bond, which consists of one sigma bond and one pi bond.

2 onsider the central carbon in this particular example also: R R R ote that the central carbon has three sigma bonds and no lone pairs. With three sigma bonds, that carbon has three groups of electrons sp 2 hybridization. The fourth orbital is a p orbital that is empty. Sp 2 hybridized atoms with three groups have a shape called trigonal planar or simply planar, and a bond angle of 120º. The new sp 2 orbitals are also asymmetric, being 33% s and 67% p, making them shorter and rounder than an sp 3 hybrid orbital. They will form stronger bonds than sp 3 orbitals because they can overlap better on the rounder lobe. Sp hybridization occurs when two groups of sigma bonds or lone pairs are present. When an atom hybridizes to sp hybridization, then two sp hybrid orbitals are formed, with two unhybridized p orbitals left over (for forming 2 pi bonds). Find the atoms with two groups : This example contains a triple bond, comprised of one sigma bond and two pi bonds Also consider the central carbon in this example: The central carbon has two sigma bonds (no lone pairs), thus two groups and is also sp hybridized.

3 These atoms have a shape called linear, a bond angle of 180º. The new sp orbitals are asymmetric like the others, comprised of 50% s and 50% p, making these the shortest and roundest of the hybrid orbitals. They will form the strongest bonds because they can overlap the best. ote the energy levels: The s orbital is most stable orbital of all and lowest in energy because the electrons in an s orbital are closest to nucleus the p orbital is least stable and highest in energy because the electrons travel furthest from the nucleus. The hybrid orbitals decrease in energy with increasing s character. verview relative Energy Levels p Energy sp 3 sp 2 sp s Practice Problem - ybridization: 1 2 Basic Questions: What orbitals constitute the 1-2 sigma bond? What orbitals constitute the 2- sigma bond? What is the geometry of? What is the bond angle between 2--? In what kind of orbital will the lone pair on be found?

4 hapter 2: (everything else) ovalent Bonds Polar ovalent Bonds Ionic Bonds (shared) (not shared) Polar ovalent Bond typically forms as a result of differences in electronegativity of atoms, causing an unequal sharing of electron pairs. δ + δ - F F Inductive Effect shifting of electrons in a sigma bond typically in response to the electronegativity of surrounding atoms Li Dipole Moment overall, net molecular polarity, including lone pair electrons and individual bond polarities. (no calculations required) Formal harge - electronic bookkeeping Positive charges. egative charges. ommonly drawn in structures. Those are FRMAL ARGES. lidocaine, hydrochloride salt l Formal harge is calculated by: (# of valence e - in free atom) ½ (all surrounding bonding e - ) (all e - in lone pairs, 2 per lone pair) F (): F (B): F --3 F B F F F (): F(): F(): º: º:

5 (Skip sections on Resonance for now.) AID-BASE EMISTRY A. Bronsted-Lowry Acid-Base Theory Acid + (proton) donor Base + acceptor This is your more traditional acid-base theory all those acids and bases you became familiar with in Gen hem (like sulfuric acid, hydrochloric acid, sodium hydroxide base). In these reactions, acids and bases react to form their conjugate bases and acids: Acid + Base onj Base + onj Acid You must be able to identify acids versus bases in any equation. ow do you determine which is the acid and which is the base? The acid always loses an +. And always remember that you can never find an acid and an acid on the same side of the equation (same goes for bases). For Bronsted-Lowry s theory, the strength of an acid is determined by how well it dissociates in the presence of water as a base, as shown here for sulfuric acid: 2S4 + 2 S r in a generic equation (A = any acid): A + 2 A otice that the products are always the conjugate base of the acid and hydronium ion, 3 +. This is an equilibrium process and not all acids donate protons equally well. The position of the equilibrium is evaluated by seeing how well an acid donates the proton to 2. The acidity constant, Ka = [A - ][3 + ] [A] Ka values range from to Strong acids favor donation due to stability of resultant anion (conjugate base). A + 2 A Equilibrium shifts to the right. Lots of product formation will lead to a large Ka Value. Because Ka values range from to 10-60, we more commonly use logarithmic relationship to express acid strengths. pka = -log Ka (inverse relationship!)

6 Strong Acids have a LARGE Ka and a SMALL pka while Weak Acids have a SMALL Ka and LARGE pka. Reminder: there is an inverse relationship between acids and bases and their conjugate bases and acids. Example: 2S4 (strong acid), S4 - (weak base)

Ch 2 Polar Covalent Bonds

Ch 2 Polar Covalent Bonds h 2 Polar ovalent Bonds Two primary bond types: ovalent (shared e -1 s) and Ionic (transferred e -1 s) Ionic bonds can have covalent character, such as with Na:l. An e -1 pair on l -1 can fill the 3s orbital