Name: _____________________________ Period: ______ Date: __________________ Unit 4 Exam – Polar/Non-­‐Polar Covalent Bonds, Ionic Bonds, Lewis Structure Directions: Carefully read what each set of directions tells you. Part 1: Electron Configuration For the following, determine: the full electron configuration AND the noble gas electron configuration. Then, calculate the total number of valence electrons in the atom. 1. Aluminum (Al) Full Electron Configuration: Noble Gas Electron Configuration: Number of valence electrons: _____ 2. Potassium (K) Full Electron Configuration: Noble Gas Electron Configuration: Number of valence electrons: _____ 3. Copper (Cu) Full Electron Configuration: Noble Gas Electron Configuration: Number of valence electrons: _____ 4. Magnesium ion (Mg+) Full Electron Configuration: Noble Gas Electron Configuration: Number of valence electrons: _____ 5. Selenium ion (Se-­‐) Full Electron Configuration: Noble Gas Electron Configuration: Number of valence electrons: _____ Part 2: Lewis Structures Determine the total number of valence electrons in the molecule. Then, draw the Lewis structure (INCLUDE PARTIAL CHARGES). Circle if the molecule is polar or non-­‐polar molecule. Finally, state the molecular geometry of the molecule. 6. N2 Total number of valence electrons: ____ Lewis Struture: (Circle one): POLAR/NON-­‐POLAR Molecular Geometry: _________________________ 7. SCl2 (Cl is a Chlorine atom) Total number of valence electrons: ____ Lewis Structure: (Circle one): POLAR/NON-­‐POLAR Molecular Geometry: ________________________________ 8. CF2O Total number of valence electrons: _____ Lewis Structure: (Circle one): POLAR/NON-­‐POLAR Molecular Geometry: _______________________________ 9. CF4 Total number of valence electrons: _____ Lewis Structure: (Circle one): POLAR/NON-­‐POLAR 10. HONORS: [N3]-­‐ Total number of valence electrons: ____ Lewis structure: (Circle one): POLAR/NON-­‐POLAR Molecular Geometry: __________________________ (Hint: think about what the shape of the molecule would be most similar to) Part 3: Ionic vs. Covalent Bonds Answer the following questions about ionic and covalent bonds 11. COVALENT bonds occur between what types of elements? 12. IONIC bonds occur between what types of elements? 13. When an ionic bond forms, the less electronegative atom becomes a _____ion. The more electronegative atom becomes a _____ion. 14. HONORS: (Circle one in sentence): In CH2F2, the molecule is considered [POLAR/NON-­‐POLAR]. In order to make the molecule as polar as possible, the 2 Hydrogens should be replaced by 2 [FLUORINES (F) / CHLORINES (Cl) / BROMINES (Br) / IODINES (I)] 15. REGULAR: Draw the Lewis structure of NaCl (Cl is Chlorine) 16. Draw the Lewis structure of MgBr2: 17. HONORS: Draw the Lewis structure of the molecule formed by bonding Magnesium (Mg) with Nitrogen (N). Part 4: Understanding the Concepts of Intermolecular Forces Answer the following questions about intermolecular forces. Show your work and be as specific as possible to receive full credit. 18. Which of the following three molecules do you think we would need to HEAT up THE MOST to turn into a gas? (Circle one): [Br2 / CBr4 / HBr] Why? 19. Water (H2O) is arguably the most important substance on Earth. a. When we heat up water to make it boil in our kitchen, we see little bubbles form at the bottom of the pot. What are these bubbles? b. Compared to many other substances on Earth, water has a very high boiling point. This means that it takes a lot of heat to turn regular water (liquid) into water vapor (gas). Explain why water is special like this. 20. Boron trifluoride (BF3) is a special molecule, because the Boron (B) atom in it is an exception to the octet rule. More specifically, Boron only needs access to six valence electrons to be stable. a. Draw the Lewis structure of BF3: b. What is the molecular geometry of BF3? (Circle one): BF3 is a [POLAR / NON-­‐POLAR] molecule. d. REGULAR: (Circle one): [H2O / CH2O / SBr2 / CH4] is likely to dissolve well in BF3. e. HONORS: The molecules below may or may not dissolve in BF3. Circle those that WILL most likely dissolve well in boron trifluoride. c.
H2O SBr2 N2 H2 CI4 CH2O CH4 HF O3 CO2 21. A molecule can have numerous different forms. While atoms within a molecule are always bonded to the same atoms, they can be bonded by different types of bonds: namely single, double, or triple bonds. Molecules that have these different forms are considered to have “resonance.” An example of a molecule with resonance is formaldehyde (CH2O). The varying forms of it are given below; CH2O’s actual molecular structure is not any one of the forms but rather a mixture of all the forms at the same time. Molecules that have resonance usually prefer one form of the molecule over the others. This is called the “primary resonance contributor.” Structure I would be the primary resonance contributor for CH2O. a. Draw the Lewis structure of NCS. Include any FORMAL charges if there are any. b. Draw ALL the resonance structures for NCS in Lewis structure format (your drawing for part a should be included in your answer). Draw the resonance structures below in the same format as above (there should be 3 structures total). Be sure to include all FORMAL charges. c. Which of the structures in part b do you think would be the primary resonance contributor? Why do you think so? d. What type of molecular geometry does the primary resonance contributor have? e. Is there another other type of molecular geometry for any of the other resonance structures? If so, state the molecular geometry of it. Part 5: Extra Credit 1. Guitar are made of two main parts: strings and a hollow wooden body. Strings are usually made of steel which is an alloy (a mixture of metals) of Iron (Fe) and Carbon (C). Performers often tune their strings on stage, but the heat from the performance lights on stage often make the guitars go out of tune after an hour. What do you think is happening to the strings and wooden body that is causing the guitar to go out of tune? 2. In this course, we have only learned about 5 different types of molecular geometries. We did not learn about other geometries where atoms can bond to more than 4 different atoms. The molecular geometry called ‘Octahedral geometry’ is when a central atom is bonded to 6 different atoms. The shape of an octahedral molecule is given below: a. One example of an octahedral molecule is SF6. How many valence electrons does the central Sulfur (S) have access to? b. Why do you think Sulfur is an exception to the octet rule? c. What charge does the central Sulfur (S) have? d. What type(s) of intermolecular forces is/are present in SF6? -­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐ 3. SURVEY: Rank as follows: 1 2 3 4 5 (Strongly Disagree) (Disagree) (Neutral) (Agree) (Strongly Agree) a. This test was easy compared to the other previous exams 1 2 3 4 5 b. I studied a lot for this test (1 would be 0-­‐10 minutes of studying. 2 would be 10-­‐30 minutes. 3 would be 30-­‐60 minutes. 4 would be 60-­‐120 minutes. 5 would be more than 2 hours). 1 2 3 4 5 c. I studied the previous quizzes, answer keys, and do-­‐nows 1 2 3 4 5 d. I always visit the website before the unit exam to study the reference guide. YES NO e. I always do my homework assignments YES NO