Atomic Theory and the Nuclear Atom Unit 2 Page 2 Atomic Theory Practice 1. Who bombarded gold foil with alpha particles? 2. Who devised the first atomic theory? 9. Who determined that the mass of an atom was concentrated in the center? 10. Who showed cathode rays are composed of negative particles? 3. Who developed the planetary model of the atom? 4. Who discovered the first subatomic particle? 5. Who discovered the nucleus? 6. Who devised the plum pudding (chocolate chip cookie) model? 7. Who was the first to suggest electrons had a fixed energy? 8. Who said that all atoms of an element are identical in size, mass and other properties? 11. Who discovered the atom is made up of mostly empty space? 12. Who had the idea of a basic indivisible particle? 13. Who concluded that all elements contain electrons? 14. Who conducted an experiment using Cathode Ray Tubes? 15. Who said atoms are neither created, nor destroyed—just rearranged? Atomic Theory and the Nuclear Atom Unit 2 Page 4-5 Structure of an Atom and Isotopes Practice Complete the following table using your knowledge of atomic structure: Element Hyphen notation Atomic Number Number of Protons Number of Neutrons Number of Electrons Mass Number 1 1 H 2 1 H 12 6 C 13 6 C 35 17 Cl 37 17 Cl 24 12 Mg 26 12 Mg 30 27 66 32 Consider the following sets of isotopes and then explain the similarities and differences between each set. Set I Set II 12 6 C 13 C 6 24 Mg 12 26 Mg 12 Atomic Theory and the Nuclear Atom Unit 2 Page 6 Average Atomic Mass Practice 1. Silicon has three, stable, naturally occurring isotopes. These are silicon-28, silicon-29, and silicon-30. The relative abundance of each is 92.21%, 4.70%, and 3.09% respectively. ESTIMATE the value of the answer before you begin. Will the weighted average be closer to 28, 29, or 30? Why? What is the average atomic mass of silicon? 2. For every 100 atoms of hafnium, 5 have a mass of 176amu, 19 have a mass of 177amu, 27 have a mass of 178amu, 14 have a mass of 179amu, and 35 have a mass of 180amu. What is the average atomic mass of hafnium? 3. Chlorine has two, stable, naturally occurring isotopes. These are chlorine-35 and chlorine-37. The relative abundance of each is 75.77%, and 24.23% respectively. What is the average atomic mass of chlorine? 127 4. Iodine is 80% 53 I, 17% 126 53 I, and 3% 128 53 I. Calculate the average atomic mass of iodine. 5. The average atomic mass of iron is 55.9002amu. Iron has four, stable, naturally occurring isotopes. Three of these isotopes are iron-54, iron-57, and iron-58. The relative abundance of each is 5.90%, 2.10%, and 0.280% respectively. What is the mass of the fourth isotope? 6. Determine the average atomic mass using the mass spec shown below. Which element is most likely shown here? 7. CHALLENGE! Calculate the average atomic mass of magnesium using the following data for three, stable magnesium isotopes. It is important to understand that the masses of a proton and neutron are approximately 1amu. Therefore, as you will notice, in the table below each isotope’s actual mass isn’t a whole number (but very close to it). Isotope mass (u) relative abundance Mg-24 23.985 78.70% Mg-25 24.986 10.13% Mg-26 25.983 11.17% Atomic Theory and the Nuclear Atom Unit 2 Page 7 Moles Practice 1. How many moles of nickel are in 82.34 grams of nickel? 2. If there are 9.32x1024 molecules of fluorine (F2), how many moles is that? 3. In 4.23 moles of magnesium, how many atoms will you have? 4. Given a sample of 2.97 moles of chlorine (Cl2), a) how many molecules of Cl2 are in your sample? b) how many atoms of Cl2 are in your sample? 5. If 13.19 moles of titanium are needed to be used to make joint replacement materials, how may grams of titanium is needed? 6. How many atoms of oxygen are in 3.12 moles of O2 (oxygen gas)? 7. What is the mass in grams of 3.00mol of the element carbon? 8. How many atoms of carbon are in 45.98g of Na? 9. How many grams are equal to 1.20x1024 molecules of Cl2?