Presentation on theme: "VSEPR Theory, Polarity, and using Electronegativity"— Presentation transcript:
1 VSEPR Theory, Polarity, and using Electronegativity Ch. 16 Covalent BondingVSEPR Theory, Polarity, and using Electronegativity
2 Covalent Bonds F F F F F F A. Types of Covalent Bonds Forms when 2 atoms share a pair of valence e-A. Types of Covalent Bonds1. Single Covalent Bond – two atoms share one pair of electronsEx: F2Unshared pair – e- not shared between atoms●●●●●●●●●●●●FFFF●●●●●●FF●●●●●●●●or●●●●●●●●●●●●●●What makes this bonding work?Atoms have 8 e- in their outer level to make them stable
3 Covalent Bonds (cont.) H H H H H H Ex: H2 ●HHH●●or●Why does H2 only need 2 e- to be stable?first energy level only contains 2 e-
4 Covalent Bonds (cont.) O O O O O O 2. Double Covalent Bond – 2 pairs of electrons are shared between atomsEx: O2●●●●●●●●OOOOOO●●●●●●or●●●●●●●●●●
5 Covalent Bonds (cont.) N N N N N N 3. Triple Covalent Bond – 3 pairs of electrons are shared between atomsEx: N2●●●●NNN●●NNN●●●●●●●●●●or●●●●●●●●
6 Covalent Lewis Dot Structures 1. Determine the # of valence e- in each atom in the molecule(# valence e- = roman numeral for group A atoms)2. The central atom is often the first atom written & is usually the atom with the least # of e-. (Exception – H can’t be the central atom). This is going to be the atom that needs to share the most electrons.
7 Lewis Dot Structures for Compounds 3. Place the electrons around the atoms so each is stable (8 around it, except H – only 2)Examples:1. Br2●●●●●●●BrBrBrBr●●●●●●●●●●●●●●●●●●
8 N N H H H H H H O C O C O O 2. NH3 3. CO2 ● ● ● ● ● ● ● ● ● ● ● ● ● ●
9 C C Cl Cl Cl Cl Cl Cl Cl Cl H H O O H H 4. CCl4 5. H2O ● ● ● ● ● ● ● ●
10 Covalent Bond Practice Problems: 1. CH OF22. H CHI33. PH CO2
11 VSEPR Theory Explains the shapes of molecules. The VSEPR theory states: b/c electrons repel each other, molecules adjust their shapes so that the valence e- pairs are as far apart from each other as possible.
12 Shape Formula Bond Angle Electrons Linear AX2 180o 4 shared 0 unshared Bent105o2 shared2 unsharedTrigonal PyramidalAX3107o3 shared1 unsharedTetrahedralAX4109.5oTrigonal Planar120oContains a double bond
13 Bond PolarityPolar Covalent Bond – when 2 atoms are joined by a covalent bond and the bonding electrons are not shared equally
14 Bond Polarity (cont.)Nonpolar Covalent Bond – when 2 atoms are joined by a covalent bond and the bonding electrons are shared equally
15 Differences between polar, nonpolar, and ionic bonds
16 How do you determine if a bond is polar, nonpolar, or ionic? Subtract the electronegativities of the bonding atoms (p. 405 in textbook)
17 Electronegativity Differences & Bond Type Type of BondElectronegativity Difference RangeNonpolar Covalent Bond0.0 – 0.4Polar Covalent Bond0.5 – 2.0Ionic Bondgreater than 2.0
18 3. Potassium and Chlorine 4. Fluorine and Fluorine Tell if the bonds between the following atoms are polar, nonpolar, or ionic:1. Hydrogen and Carbon2. Oxygen and Carbon3. Potassium and Chlorine4. Fluorine and Fluorine5. Nitrogen and OxygenH 2.1C 2.50.4 NonpolarO 3.5C 2.51.0 PolarK 0.8Cl 3.02.2 IonicF 4.00.0 NonpolarN 3.0O 3.50.5 Polar
19 Polarity of MoleculePolar Molecule – a molecule with a positive and negative end. Polar bonds must be present.
20 Polarity of Molecule (cont.) It is possible to have polar bonds but not a polar molecule!Carbon dioxide has 2 polar bonds and is linear.Bond polarities cancel out b/c they are in opposite directions.CarbonOxygenOxygen
21 Practice:Write the dot structure of the following molecules – then predict the shape and polarityI2PCl3H2SCHI3SiO2CH2O