CHM 1430 Study Guide - Final Guide: Lewis Structure, Bond Length, Molecular Geometry

Map do Sapling Learning Draw a Lewis structure for SO2 in which all atoms obey the octet rule. Show formal charges. Do not consider ringed structures. Almost on this first structure. Find the formal charge on an atom in a Lewis structure by subtracting the number of valence electrons the atom actually contributes contribute. To determine the number of electrons contributed by an atom, count the number of electrons around each atom. Remember that the two electrons shared in a bond count as one electron for each atom. Both oxygen and sulfur are expected to contribute six electrons. Draw a Lewis structure for SO2 in which all atoms have a formal charge of zero. Explicitly showing the zero charges is optional. Do not consider ringed structures.

STRC 434: Wricing Lewis Symbols and Lewis Strucnures (4) Write the Lewis structure for the ionic com 5. Construct the Lewis structure model for the cova pound potassium chioride in the box. lent compound sulfur difluoride (SF2) using the tollow ing steps (1) atom is The number of valence electrons in the sulfur . The total number of valence electrons is the total Lewis structure of potassium chloride How does the written Lewis structure for po, in the two fluorine atoms isHence number ol valence electrons in SF's (5) tassium chioride differ from that ot hydrogen chloride? (2) Arrange the atomic cores for the two fluorine atoms with the sultur atom as the central atom in the space below. (3) Rewrite the atomic cores in the space below. Place an electron pair between each fluorine and sulfur core. Write the Lewis structure for SF2 in the box, lent compound hydrogen sulfide (H2S) using the fol- distributing the remaining valence electrons so that all 4. Construct the Lewis structure model for the cova- (4) lowing steps. three atoms are in accordance with the octet rule. (1) The total number of valence electrons in the two hydrogen atoms is ; the sulfur atom has Hence, the total number of valence electrons in the compound is Lewis structure of SF2 (2) Write the atomic cores for the hydrogen atoms and the sulfur atom in the space below. Because sulfur is the central atom in this molecule, ar- range the cores so that the hydrogen atoms are on ei ther side of the sulfur atom. 6. Construct the Lewis structure model for the cova- lent compound methylene chloride (CH2C) The number of valence electrons in the car- The total number of valence elec (1) bon atom is trons in the two hydrogen atoms is number of valence electrons in the two chlorine atoms is trons in CH2C12 is The total (3) Rewrite the atomic cores in the space below. Place an electron pair between each hydrogen atom and the suilfur atom. Hence, the total number of valence elec- (2) Position the atomic core for carbon as the (4) Write the Lewis structure for hydrogen sulfide central atom in the space below, and place the other in the box, distributing the remaining valence electrons cores around it so that the hydrogen atoms are in accordance with the duet rule and the sulfur atom is in accordance with the octet rule. (3) Rewrite your arrangement of atomic cores ir the space below, joining the cores with electron pairs to form the necessary bonds. Lewis structure of H2S

Lewis structures of some molecules with multiple bonds Multiple bonds are represented with more than one straight line between atoms. A double bond is formed when two atoms share two pairs of electrons and is stronger than a single bond. A triple bond s formed when two atoms share three pairs of electrons and is stronger than a double bond. What is the total number of electrons shown in the Lewis structure in Model 5 for each molecule? Compare your answers to CTQs 19 and 21. How does one determine the total number of electrons that should be used to generate a Lewis structure? For N_2, is the sum of the bonding electrons and the lone pair electrons around each N atom consistent with the Lewis model? In other words, does each N have an octet? Write a sentence to explain. For H_2CO: a. Is the sum of the bonding electrons and the lone pair electrons around each C atom consistent with a complete octet? b. Is the sum of the bonding electrons and the lone pair electrons around each 0 atom consistent with a complete octet? Using the information from above, construct a checklist that can be used to determine if a Lewis structure for a molecule is correct. Try to think of at least three criteria. Compare your criteria with your team and try to come to agreement. List any questions that remain with your team about Lewis dot structures.