POGIL EXERCISE 04 Anatomy and Physiology of the Atom

Transcription

1 RUN TIME: 60 MIN POGIL 4 Page 1 of 8 POGIL EXERCISE 04 Anatomy and Physiology of the Atom Each member should assume his or her role at this time. The new manager takes charge of the POGIL folder and hands out the GRF and RRF to the appropriate members. The new recorder should record the names of the group members on the new GRF. Table 1. Group Member Role Assignments GROUP TYPE -> GROUPS OF THREE GROUPS OF FOUR MEMBER NO. -> Manager + + Reporter + + Recorder + + Reflector + + Technician Encourager + + SFUC + * + The manager should direct the group to read Observation I below and then direct the group to begin processing with Item 1: OBSERVATION I: The atom is the smallest unit of an element that still retains the chemical and physical properties of that element; however, the atom is not the smallest unit of matter. Atoms are made up of even smaller pieces of matter called subatomic particles. There are three primary subatomic particles: protons, neutrons, and electrons (Table 2). The protons and neutrons are located in the center of the space occupied by the atom; this center area is referred to as the nucleus of the atom. The electrons orbit the nucleus in a manner that is often simulated as a cloud in diagrams in modern chemistry books not in planar orbits often depicted in older texts. Physicists and chemists have a particular type of code to quickly identify the exact number of protons, electrons and neutrons in an atom. This code is deciphered for you by Figure I. Table 2. Major Subatomic Particles and Their Properties and Atomic Locations NAME MASS (AMU*) CHARGE LOCATION DETERMINES Electron 5.6 X Outside the nucleus Chemical Reactivity Neutron 1 0 Nucleus Isotope Proton 1 +1 Nucleus The element *Atomic Mass Unit (AMU) equals 1.7 x grams +5 MIN

2 RUN TIME: 60 MIN POGIL 4 Page 2 of 8 Figure I. Standard Atomic Notation Format *If this notation is not shown, the charge is zero. **Often not written because it can be obtained from periodic chart. 1. What do the initials AMU stand for? Why do you think this special unit is used by chemists if the actual mass is known in grams? 2. What is the mass in grams of an electron? 3. According to Table 2, what two subatomic particles have the same mass? 4. What conclusion can be drawn about the mass distribution in an atom? 5. The helium atom is composed of 2 protons, 2 neutrons and two electrons. Draw a modern diagram of the atom in Figure II to the right consistent with diagrams in Chapter 4 & 11 of the text. Have instructor examine the diagram. 6. The atomic mass number (A) of an atom is the mass of the atom in AMU to the nearest whole number. What is the atomic mass number for this helium atom? 7. Write an Equation (EQ1) below that would calculate A of any element given the specific number of major subatomic particles. Figure II. Modern Diagram of Helium Atom EQ1: A = Recorder should present the group s work to instructor for validation. +15 MIN

3 RUN TIME: 60 MIN POGIL 4 Page 3 of 8 OBSERVATION II. The number of Protons in the nucleus determines the element to which the atom belongs; the number of protons is referred to as the atom s atomic number (Z). This means that all atoms that have the same atomic number have the same chemical properties and belong to the same element. However, all atoms of the same atomic number may not have the same atomic mass number. This means that although they have the same number of protons, they may have different number of neutrons and thus different atomic mass numbers. Atoms that have the same atomic number but different atomic mass numbers are called isotopes. You will recall that the nucleus of the atom contains all the protons and neutrons of the atom; therefore, all most all of the mass and all of the positive charge resides in the center of the atom. The function of the neutrons is believed to be that they prevent the nucleus from flying apart due to the repulsion of like charges. Evidence for this proposal is that the larger the atomic number the higher the ratio of neutrons to protons. 8. What is the charge associated with the nucleus? 9. Using the information in Observations I and II, the periodic table at the end of this exercise, and Row 1 of Table 3, fill in the blank cells of Table 3. Table 3. Comparison of Atomic Mass to Ratio of Neutrons to Protons. ELEMENT Number of Number of N Name Symbol Neutrons (N) Protons (Z) P Helium-4 4 He Ne Argon Kr Xenon-131 Radon Recorders should present Table 3 to the instructor for validation. 10. Plot in Figure III the values of N/P for neon through radon calculated in Table 3. Draw the best straight line through the points using a straight edge. +25 MIN

4 RUN TIME: 60 MIN POGIL 4 Page 4 of 8 Figure 3. Relationship of Neutrons to Protons as Atomic Mass Increases 11. Do the data in Table III and Figure III support the observation made in the first part of Observation II concerning the relationship between protons and neutrons? Explain your answer: Recorders should present their diagram to the instructor for validation before the group continues processing by reading Observation III. OBSERVATION III. The number of electrons in the atom determines the charge of the atom. The charge of an atom (C) is equal to the number of protons minus the number of electrons. Elemental atoms have a charge of zero because in the elemental form the number of protons and electrons are equal. However, in a chemical reaction electrons are either donated and accepted or shared between the elemental atoms involved in the reaction. In the case where electrons are donated and accepted the atom becomes charged; a charged atom is called an ion. When an atom gains electrons, it becomes negatively charged and is called an anion. When an atom loses electrons, it becomes positively charged and is called a cation. One more concept about electrons you should know: the arrangement of the electrons around the nucleus determines the chemical properties of the element. This will be directly covered in a future POGIL; moreover, everything else in chemistry is related to the electron arrangement. +35 MIN

5 RUN TIME: 60 MIN POGIL 4 Page 5 of Write a mathematical expression (Equation 2) that can be used to calculate the charge (C) of any atomic species. EQ2: C = 13. Using information from the periodic table at the end of this exercise, Observation III and Row 1 of Table 4, fill-in the values for the blank cells in Table 4. Table 4. Determining the Type and Charge of Various Atomic Species Atomic Species Name* Symbol Number of Protons Number of Electrons Charge Classification** Chloride-36 ion Cl anion Silver Si 14 Oxide-16 ion P 15 *All ion names must include the word, ion, in the name as shown in Row 1. In addition, anion first name is formed by using the elemental stem + ide as shown in Row 1. The cation s first name is just the name of the element; e.g., Cs + is named the cesium ion. **Classify as either an atom (E), cation (C), or anion (A). +40 MIN

6 RUN TIME: 60 MIN POGIL 4 Page 6 of Using the information gathered from all previous sections, complete Table 5. Table 5. Basic Properties of Selected Atomic Species. ROW Species Name Symbol Number Protons Number Neutrons Atomic Mass Number Electrons Charge 1 Chloride-36 ion 36 Cl Sodium-23 ion C Na Recorders should present the group s Table 3 to the instructor for validation. Managers should resume processing once the results have been verified. +50 MIN

7 RUN TIME: 60 MIN POGIL 4 Page 7 of Isotopes of an element have the same atomic number but different atomic masses. List below the atomic species in Table 5 that are isotopes. List them by symbols in their elemental groups. 16. How do you know from the name of the species whether it is charged or not? 18. How do you know from the name of an atomic species whether or not it is negatively charged? 19. How do you know from the name of an atomic species whether or not it is positively charged? EXERCISE END. Managers should collect the GRF, the Recorders exercise and the RRF, paperclip them together, and place in the left pocket of the folder. The folder should be closed and left on the table. +60 MIN

8 RUN TIME: 60 MIN POGIL 4 Page 8 of 8