CHM151 C10 C12 Molecular Bonding Shape Really Matters 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding Objectives Review Lewis Structures ABnEn 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms A. The element symbol is drawn to represent the nucleus and core electrons B. The valance electrons are drawn around the symbol—one on each side before doubling up C. Exceptions to the Octet Rule 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms C. Exceptions to the Octet Rule 1. Most atoms are the most stable with 8 electrons in their valence shell, and will bond until this is reached. 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms C. Exceptions to the Octet Rule 2. However, hydrogen and helium can only hold 2 electrons in their valence shell. 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms C. Exceptions to the Octet Rule 3. Boron and Beryllium can be stable with only 6 valence electrons 4. Any element in the third row or below can hold more than 8 in the empty d subshells. 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms D. Arranging atoms in a Lewis Structure 1. It is often difficult to know in what order to place the atoms.  There are some general rules that can be followed: 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms a. For molecules with only 2 elements, arrange the atoms symmetrically b. “COOH” is a carboxylic acid (both O’s bond to the C and the H goes on one of the O’s) c. Hydrogen and halogens cannot go in the middle d. Write the remaining atoms in the order they appear in the formula e. Write the hydrogen and halogen atoms around the element they are written next to in the formula 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms E. Drawing Lewis Structures for covalent compounds 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms Arrange the atoms as above. Determine the total # of valence electrons for the whole molecule Put one bonding pair between each set of atoms to be bonded. Place remaining electrons in lone pairs, starting with the most electronegative element. If atoms do not have full valence shells, move a lone pair from an adjacent atom in to double, or triple, bond. 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms F. IE 1. ammonia, NH3 2. Nitrogen atom has 5 valence electrons 3. Hydrogen atom has 1 valence electron . . ∙N∙ ˙ H∙ 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms F. IE 4. Each of the 3 hydrogen atoms will share its electron with nitrogen to form a bonding pair of electrons (covalent bond) so that each hydrogen atom has a share in 2 valence electrons (electronic configuration of helium) and the nitrogen has a share in 8 valence electrons (electron configuration of neon) Lewis Structure (electron dot diagram) for ammonia 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Review Lewis Structures I. Lewis Structures of atoms F. IE 5. DONE . . H∙∙N∙∙H ˙ ˙ H 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding ABnEn II. ABnEn A. The shape of a molecule is determined by minimization of the electron clouds that surround a central atom 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding ABnEn II. ABnEn B. The atomic orbitals of the central atom have hybridized, with the hybrid orbitals arranging themselves in the shape that minimizes the repulsions of electrons occupying these hybrid orbitals. 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding ABnEn II. AXnEn or ABnEn C. ABnEn 1. A is the central atom 2. B or X is the ligand or atom bonded to central atom 3. n is the number of ligands bonded to X 4. E is lone pairs 5. n is the number of lone pairs 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding ABnEn II. ABnEn D. Valence Shell Electron Pair Repulsion Theory 1. Bonds are made of electrons and electrons are negative and therefore repel each other. 2. Bonds and lone pairs form as far apart from each other as possible. 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding ABnEn II. ABnEn E. AB2E0 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding ABnEn II. ABnEn F. AB3E0 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn G. AX4 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn H. AX2E1 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn I. AX3E1 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn J. AX2E2 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn K. AX5E0 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn L. AX4E1 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn M. AX3E2 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn N. AX2E3 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn O. AX6E0 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn P. AX5E1 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding AXnEn II. AXnEn Q. AX4E2 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

CHM151 C10 C12 Molecular Bonding A Brief Review Review Lewis Structures AXnEn 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding

Tonight’s Opportunity CP Lab- Total Valence electrons, Draw Lewis Structures, Determine ABnEn CP Lab- Hybridization, Electrical& Molecular Geometries, Draw Molecular Picture, Determine Bond Angles 1/18/2019 11:23 AM CHM151 C10 C12 Molecular Bonding