3What is the electron configuration of carbon? Warm-UpWhat is the electron configuration of carbon?How many valence electrons does Carbon have?1s22s22p24
4To determine the Lewis dot structure for Carbon we look at the number of valence electrons carbon has. Carbon has four valence electrons and we represent electrons as DOTS.C
5Lewis Dot Structures for the first 10 elements on the periodic table.
6Chemists use Lewis Dot Structures to determine how elements are covalently bonded to each other in a molecule.Covalently Bonded means to share electrons between elements. Sharing of electrons occurs between a nonmetal and another nonmetal.Single Bond- 2 electrons are sharedDouble Bond- 4 electrons are sharedTriple Bond- 6 electrons are shared
7Draw the Lewis Dot structure for BeF2. Count the number of valence electrons you have to work with.BeFTotal : valence electrons2. Put the least electronegative element in the center (remember the trend of E.N)**One exception: we never put Hydrogen in the center, because it can only make one bond.Use pairs of electrons to form bonds between all atoms. (2 electrons make one bond)Use the remaining electrons to complete the octet rule for each element. (Exception: Be disobeys the octet rule it only has two valence electrons)If you run out of electrons, you must introduce multiple bonds to maintain the octet rule. (BeF2 does not have multiple bonds-we will do more examples of this)
9Let’s try to draw a Lewis Dot Structure of CO2 using the Rules Count the number of valence electrons you have to work with.COTotal : valence electrons2. Put the least electronegative element in the center (remember the trend of E.N!!!?)Use pairs of electrons to form bonds between all atoms. (2 electrons make one bond)Use the remaining electrons to complete the octet rule for each element.If you run out of electrons, you must introduce multiple bonds to maintain the octet rule.OCO
12This gives rise to different molecular shapes. Valence Shell Electron Pair RepulsionVSEPRElectron pairs surrounding an atom want to be as far apart from each other as possible.This gives rise to different molecular shapes.
14The simplest shape is a LINE Alkali Metals and Halogens make a line because they can only bond once.Groups 1 and 17 make a line
15The electron pairs are the farthest apart they can be. Let’s look at another simple molecular shapeThe electron pairs are the farthest apart they can be.This molecule is LINEARThe center atom bonds twice.Elements in group 2 make linear structures.
16How is the Be atom able to covalently bound to the fluorines? Hybridization of the orbitals explains this.Two or more of the orbitals of the central atom must mix to form new orbitals of equal energy so bonding can take place.Fill in valence electronsHybrid mixingsp2pA linear molecule has sp hybridization2s
18Group 13 makes a trigonal planar shape BH3Draw Lewis Structure:This arrangement lets all the electron pairs be the furthest apart from each other.Group 13 makes a trigonal planar shape
19Draw electron diagram for B Hybrid mixingspp2p2sA trigonal planar molecule has a sp2 hybridization
20Group 14 makes tetrahedral shapes. What does the word ‘tetra’ mean?CH4 MethaneStructure:This arrangement lets all the electron pairs be the furthest away from each other.Group 14 makes tetrahedral shapes.
21Draw the electron diagram of Carbon What do you think is the hybridization of tetrahedral molecules??2p2s
22Trigonal PyramidalNH3This arrangement lets all the electron pairs be the furthest apart from each other. With one lone pair.This is similar to the tetrahedral arrangement ,but has one lone pair.Group 16 makes Trigonal Pyramidal Shapes
23What is the hybridization of NH3( trigonal pyramidal) Fill in valence electrons for Nitrogen2p2s
24Group 15 makes bent shapes. H2OThis arrangement lets all the electron pairs be the furthest apart from each other. With two lone pairs.What is the hybridization of the bent molecule? Do you think it will be similar to tetrahedral?Group 15 makes bent shapes.
25What is the hybridization of H20? (bent shape) Fill in valence electrons for oxygen2p2s
26VSEPR Theory Summary Shape #of atoms Hybridization Examples Linear 2 spCO2Trigonal Planar3sp2BH3Tetrahedral4sp3CH4Trigonal Pyramidal3 with one lone pairNH3Bent2 with two lone pairsH2OGroup 2Group 13Group 14Group 15Group 16
27Polarity of MoleculesWe can determine if a molecule is polar or nonpolar by the molecule’s shape.In some covalent bonds electrons are not shared equally between the elements.The more electronegative element ‘WINS’ the electrons.The charge difference across the bond as well as the shape of the molecule results in a POLAR Molecule.
28Polarity of WaterPolar molecules act as tiny dipoles because they have un even charges.A dipole is created by equal but opposite charges that are separated by a short distance.Direction of dipole is from positive end to more negative end (more electronegative element)Lets take water for example:Because WATER is a BENT Molecule the polarities of each bond add together to make this molecule highly POLAR
29What about NH3 Trigonal Pyramidal POLAR OR NONPOLAR?The dipoles of the three bonds are additive combining to form an overall net dipoleBecause NH3 is trigonal pyramidal shape it is POLAR
30OVERALL the molecules are NONPOLAR. CH4CO2The individual bond polarities extend equally and symmetrically in different directions canceling out .OVERALL the molecules are NONPOLAR.
31What about CH3Cl? NonPolar or Polar? Try with a partner…ClHHHPOLAR