CHEM 219 EXAM 1

On a piece of scratch paper, write out the Lewis Dot Diagram for each of the indicated elements and determine the following for each: a) The number of Lone Pairs the atom possesses in its valence shell. b) The number of Unpaired Electrons the atom possesses in its valence shell. c) The number of bonds the atom will form. Oxygen Carbon Hydrogen Nitrogen - Answer-Oxygen - a) 2 b) 2 c) 2 Carbon - a) 0 b) 4 c) 4 Hydrogen- a) 0 b) 1 c) 1 Nitrogen - a) 1 b) 3 c) 3 Classify the bonding between the given pairs of atoms as ionic, covalent, or polar covalent. Use the table of electronegativities shown below to help with the classification. a. Br and Br b. K and Cl c. P and Cl d. C and O e. Na and Br - Answer-a. Br-Br: Electronegativity difference () = 0 = COVALENT (or pure covalent) b. K-Cl: () = 2.2 = IONIC c. P-Cl: ()= 0.9 = POLAR COVALENT d. C-O: ()= 1.0 = POLAR COVALENT e. Na-Br: () = 1.8 = POLAR COVALENT Define the term constitutional isomer. - Answer-Two (or more) different chemical compounds with the same molecular formula but different connectivity between the atoms in their structural formulae. Explain (using specific evidence) what makes the following two compounds constitutional isomers of one another: - Answer-Both compounds have a MF of C3H6O - same MF