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5/17/2015 Review Topic 3: Elements, Radioactivity, and the Periodic Table Name: Score: 19 / 19 points (100%) Review Topic 3: Elements, Radioactivity, and the Periodic Table Multiple Choice Identify the choice that best completes the statement or answers the question. A 1. The element chlorine exists as two naturally occurring isotopes. Cl35 occurs 75% of the time and Cl37 occurs 25% of the time. Which of the following calculations should be used to calculate the correct average atomic mass of chlorine? a. (35 amu x 0.75) + (37 amu x 0.25) c. (35 amu x 3) + 37 amu 3 b. (35 amu x 3) + 37 amu d. 35 amu 37 amu 2 2 ANSWER: A We learned each amu x %, add them together then divide by 100. The correct answer here just divided each percent by 100 first. POINTS: 1 / 1 B 2. Radioactive iodine131 has a halflife of eight days. The amount of a 200.0 gram sample left after 32 days would be — a. 6.25 g c. 25.0 g b. 12.5 g d. 50.0 g ANSWER: B Total time = # x half life time 32 = # x 8 # = 4, so we need to divide 200.0 grams by 2 four times. 200/2/2/2/2 = 12.5 POINTS: 1 / 1 A 3. Which of these describes a tendency for atomic radii as displayed on the periodic chart? a. Atomic radii decrease left to right across a period. b. Atomic radii increase left to right across a period. c. Atomic radii decrease top to bottom down a group. d. Atomic radii increase, then decrease from top to bottom down a group. ANSWER: A radii gets bigger going down and smaller going across (left to right), so Fr is biggest and F is smallest. (Opposite trend of electronegativity) POINTS: 1 / 1 C 4. How does the radioactive isotope C14 differ from its stable counterpart C12? a. It has a different number of protons and two less neutrons than C12. b. It has the same number of protons and two more electrons than C12. c. It has the same number of protons but two more neutrons than C12. d. It has a different number of protons and two more neutrons than C12. file:///C:/Users/Joseph%20Morris/Desktop/SOL%20Review%20Topics/Review%20Topic%203/review_topic_3_sg.htm 1/6 5/17/2015 Review Topic 3: Elements, Radioactivity, and the Periodic Table ANSWER: C What makes isotopes neutrons It has a different number of protons and two less neutrons than C12. different protons would change it from C It has the same number of protons and two more electrons than C12. different electrons would make it an ion, not an isotope It has the same number of protons but two more neutrons than C12. two more neutrons would make it 2 heavier and make it 14. It has a different number of protons and two more neutrons than C12 . different protons would change it from C POINTS: 1 / 1 D 5. Chlorine forms a 1– ion. How many electrons does a chloride ion have? a. 1 c. 17 b. 16 d. 18 B 6. ANSWER: D Normally, Cl has 17 electrons. 1 means that it has gained another electron, which are negative to make the total 18 POINTS: 1 / 1 6. Which of the groups below has the electron dot structure shown above? a. Noble gases c. Alkali metals b. Halogens _ d. Transition elements ANSWER: B Looking for a group with 7 valence electrons sends us to group 17 the halogens POINTS: 1 / 1 A 7. Which of these elements is the most chemically active? a. F c. Br b. Cl d. I A 8. ANSWER: A Fluorine is the most electronegative which makes it the most reactive. Francium, the least electronegative, believe it or not is up there for reactivity as well. POINTS: 1 / 1 Element Protons Neutrons Electrons 1 20 20 20 2 40 40 40 file:///C:/Users/Joseph%20Morris/Desktop/SOL%20Review%20Topics/Review%20Topic%203/review_topic_3_sg.htm 2/6 5/17/2015 Review Topic 3: Elements, Radioactivity, and the Periodic Table 3 4 20 20 10 20 10 40 Which above represents an atom of calcium? a. 1 c. 3 b. 2 d. 4 ANSWER: A Calcium has an atomic number of 20. which means it would have 20 protons and since it is an atom and not an ion, the electrons would be equal to the protons. POINTS: 1 / 1 A 9. From left to right across a period, what change is occurring within the atomic nuclei? a. A proton is gained c. A neutron is lost b. An electron is gained d. The electron cloud size is decreasing ANSWER: A Electrons and the electron cloud are not in the atomic nuclei and neutrons would be gained. POINTS: 1 / 1 B 10. A scientist has found the following isotope of oxygen How many neutrons are present in this isotope? a. 8 c. 19 b. 11 d. 27 ANSWER: B Top number is the mass number, bottom number is the atomic number. Neutrons = mass number atomic number = 198 = 11 POINTS: 1 / 1 A 11. The elements that are characterized by the presence of an incomplete d sublevel are called a. transition elements c. halogens b. alkali earth metals d. lanthanoids ANSWER: A transition elements incomplete d alkali earth metals incomplete s halogens incomplete p lanthanoids incomplete f POINTS: 1 / 1 D 12. The net charge on an aluminum ion is +3 because there are a. 10 protons and 13 electrons in the atom b. 13 protons and 10 neutrons in the nucleus c. 10 neutrons and 13 electrons in the atom d. 13 protons and 10 electrons in the atom ANSWER: D file:///C:/Users/Joseph%20Morris/Desktop/SOL%20Review%20Topics/Review%20Topic%203/review_topic_3_sg.htm 3/6 5/17/2015 Review Topic 3: Elements, Radioactivity, and the Periodic Table Al has 13 protons (atomic number) and since it is +3, there has to be 3 more protons than electrons. Changing the neutrons would only change the mass and the isotopes. POINTS: 1 / 1 A 13. How many protons, neutrons, and electrons are in a neutral atom of sodium? a. 11 p+, 12 n0, 11 e c. 12 p+, 11 n0, 12 e + 0 b. 11 p , 11 n , 12 e d. 12 p+, 11 n0, 11 e ANSWER: A Sodium is atom #11, which means it has 11 protons and since it is neutral it needs 11 electrons. POINTS: 1 / 1 A 14. Which conclusion can be made from these data? Characteristics of Different Sulfur (S) atoms 1 2 3 4 Protons 16 16 16 16 Neutrons 16 17 18 20 Electrons 16 16 16 16 a. Different isotopes of sulfur (S) have different number of neutrons. b. Different polymers of sulfur (S) have different numbers of electrons. c. All ions of sulfur (S) have the same mass. d. All particles of sulfur (S) have the same mass number ANSWER: A Changing neutrons results in isotopes which is what we see in this chart (the neutrons changed) Different electrons result in ions not polymers If the neutrons are different in the ions, then the masses would change Once again, if the neutrons are different then the mass number would be different POINTS: 1 / 1 A 15. Which element has atoms that most likely have the greatest shielding effect? a. Barium (Ba) c. Calcium (Ca) b. Strontium (Sr) d. Magnesium (Mg) ANSWER: A The more electrons you have and the bigger the atom (more energy levels) the more shielding it would have. POINTS: 1 / 1 B 16. Which element has 16 neutrons, 15 protons, and 15 electrons? a. Sulfur (S) c. Gallium (Ga) b. Phosphorus (P) d. Zinc (Zn) ANSWER: B The important subatomic particle here is the proton. The number of protons = atomic number, which tells you the element is phosphorus (atomic number 15). POINTS: 1 / 1 file:///C:/Users/Joseph%20Morris/Desktop/SOL%20Review%20Topics/Review%20Topic%203/review_topic_3_sg.htm 4/6 5/17/2015 Review Topic 3: Elements, Radioactivity, and the Periodic Table A 17. Consider any set of three elements in the same period on the periodic table. For which characteristics is the average for the three elements always equal to the value of the middle element? a. Atomic number c. Number of neutrons b. Atomic mass d. Number of isotopes B 18. ANSWER: A Since atomic number always increases by 1 as you increase elements, this is the only characteristic that is listed that is consistent enough to have the average work. POINTS: 1 / 1 What is the halflife of Americium242? a. 11 hours b. 16 hours c. 32 hours d. 64 hours ANSWER: B A halflife is the amount of time required to lose half of your material. According to the graph, it takes 16 hours to go from 80 to 40. POINTS: 1 / 1 Multiple Response Identify one or more choices that best complete the statement or answer the question. Directions: Click on the correct answers. 19. According to the periodic table of the elements, which elements belong to the same period? a. Aluminum d. Arsenic b. Germanium e. Gallium c. Antimony RESPONSE: B,D,E ANSWER: B,D,E file:///C:/Users/Joseph%20Morris/Desktop/SOL%20Review%20Topics/Review%20Topic%203/review_topic_3_sg.htm 5/6 5/17/2015 Review Topic 3: Elements, Radioactivity, and the Periodic Table POINTS: A row is known as a period, so we need all the elements in the same row. 1 / 1 file:///C:/Users/Joseph%20Morris/Desktop/SOL%20Review%20Topics/Review%20Topic%203/review_topic_3_sg.htm 6/6