Name: Date: Period: Chemistry POGIL: Ions WHY? There is a significant difference in reactivity between an atom and its respective ion. For instance, elemental sodium reacts violently with water to produce hydrogen gas and sodium hydroxide, a caustic base. http://www.metacafe.com/watch/780542/reaction_of_sodium_with_water/ Sodium ions on the other hand are quite delicious when applied to French fries. If sodium ions reacted as violently with your saliva as the neutral atoms do with water, you would explode your mouth. In this POGIL, we will learn how to determine if an atom is neutral or ionic, and how to calculate the numbers of protons and electrons from atomic and ionic symbols. SUCCESS CRITERIA: Identify the composition of atoms and their ions in terms of the numbers of protons, neutrons, and electrons. Use atomic symbols to represent different atoms and their ions. Utilize the Periodic Table of Elements as a resource. PREREQUISITES: Identify subatomic particles protons, neutrons, and electrons by their characteristics and location in the atom. RESOURCES: Periodic Table of Elements Laptop (for WHY? video) VOCABULARY: Cation = positively charged ion Anion = negatively charged ion
Model 1: Atoms and Ions P O G I L : I o n s Page 2
P O G I L : I o n s Page 3 Key Questions 1. Use Model 1 and the Periodic Table to complete the following table. Element Metal / Nonmetal # of p + the same for atom & ion? # of n 0 the same for atom & ion? # of e - the same for atom & ion? Ionic Charge Lithium metal 1+ Magnesium Aluminum YES Fluorine Oxygen NO nonmetal YES NO Nitrogen 3-2. Based on the table, what distinguishes a neutral atom from an ion? 3. Examine the isotope symbols in Model 1. a. Where is the ion charge located in the isotope symbol? b. Is a charge indicated on the neutral atoms? If yes, how and where? 4. Which subatomic particle carries a positive charge? 5. Which subatomic particle carries a negative charge? 6. Propose a mathematical equation to calculate the charge of an ion from the number of protons and electrons in an ion. Confirm that your equation works by verifying two positive ion examples and two negative ion examples from Model 1.
P O G I L : I o n s Page 4 7. Chemists refer to positively charged ions at cations, and negatively charged ions as anions. Complete the following table. Symbol Atomic Number Mass Number Charge Number of Protons Number of Neutrons Number of Electrons Cation / Anion 8. Could a +3 ion of aluminum be made by adding three protons to an aluminum atom? Explain. 9. One of your classmates is having trouble understanding ions. He explains the formation of a cation like this: When you add an electron, you get a positive charge because adding is positive in math. a. Explain in a grammatically correct sentence why this student is incorrect. b. Provide a better description of how math relates to electron and ion formation.
P O G I L : I o n s Page 5 Model 2 Ion Charges for Selected Elements Key Questions 10. Draw a star-step line in Model 2 to separate the metals and nonmetals. (Consult a Periodic Table.) 11. Consider the ions listed in Model 2. a. In general, do metals form anions or cations? b. In general, do nonmetals for anions or cations? c. What is unique about some of your transitional elements? Exercises 12. Choose the correct statement: a. Metals make positive cations and nonmetals make negative anions. b. Metals make negative cations and nonmetals make positive anions. c. Metals make positive anions and nonmetals make negative cations. d. Metals make negative anions and nonmetals make positive cations. 13. What is the charge of an ion with 21 protons, 30 neutrons, and 18 electrons? a. 4+ b. 3+ c. 4- d. 4+
P O G I L : I o n s Page 6 14. The diagrams below show representations of atoms ions for sodium and fluorine. (Note: Diagrams are not to scale.) 11 protons 12 neutrons 11 protons 12 neutrons 11 electrons Sodium Atom Sodium Ion 10 electrons 9 protons, 10 neutrons 9 protons 10 neutrons 9 electrons 10 electrons Fluorine Atom Fluoride Ion a. Write nuclide symbols for each atom and ion. ATOM/ ION NUCLIDE SYMBOL Sodium Sodium Ion Fluorine Fluoride Ion b. What do the two ions have in common? c. Referencing the Periodic Table of Elements, what neutral atom has the same number of electrons as the two ions in Model 2?