HN HW: The Atom

1. Fill in the blanks Element Atomic # Mass # Protons Neutrons Electrons Lithium (Li) 3 7 3 4 3 Chlorine (Cl) 17 35 17 18 17 Silver (Ag) 47 108 47 61 47 Lead (Pb) 82 207 82 125 82 Selenium-79 34 79 34 45 34 Argon-39 18 39 18 21 18 232Th 90 232 90 142 90 209Po 84 209 84 125 84 2a. Which statement(s) in Dalton’s atomic theory is now considered to be incorrect? Atom is a solid sphere which cannot be broken down to smaller particles. All atoms of a given element are identical (same size, mass, chemical properties). For example, atoms of hydrogen are different from atoms of oxygen. Atoms can chemically combine in whole-number ratios to form compounds. Chemical reactions occur when atoms are separated, joined, or rearranged. 2b. Describe how the modern atomic theory differs from the statements you chose in 2a. 3. Compare and contrast Thomson’s plum pudding atomic model with Rutherford’s nuclear atomic model Plum Pudding Model atoms are solid spheres atoms are positively charged electrons and mass evenly dispersed throughout the atom Nuclear Model majority of the mass is contained in the nucleus electrons scattered outside of the nucleus mostly empty space small, positive nucleus 4. What caused the deflection of the alpha particles in Rutherford’s gold foil experiment? scattered electrons small, dense, positive nucleus neutral neutrons 5. Which subatomic particle was discovered by researchers working with a cathode ray tube? proton neutron electron 6. Which subatomic particle tells us what type of element we have? How is this particle related to the atom’s atomic number? 7. Which subatomic particles account for most of an atom’s mass? protons neutrons electrons 8. Explain how the existence of isotopes is related to atomic masses not being whole numbers. 9. Can two atoms with the same mass number ever be isotopes of each other? Explain. 10. Nitrogen has two naturally occurring isotopes, N-14 and N-15. The atomic mass of nitrogen is 14.007 amu. Which isotope is more abundant in nature? Explain your answer. 11a. Use the data from the four isotopes below to calculate the transition metal’s average atomic mass. Show your work by typing in your calculations below or upload a picture if you're showing your work on paper. 11b. Identify the element from question 11a (provide the name, not the symbol): chromium 12. Percent Abundance Boron has two naturally occurring isotopes. Boron-10 has an atomic mass of 10.013 amu; boron-11 has an atomic mass of 11.009 amu. The average atomic mass of boron is 10.811 amu. What is the percentage of naturally occurring boron-10? Show your work.