6:19 1 LTE Ch 2 Textbook Probl... I1. Uranjum-235 is the isotope of uranium commonly used in nuclear power plants. How many (a) protons are in its nucleus? (b) neutrons are in its nucleus? (c) electrons are in a uranium atom? 12. An isotope of americium (Am) with 146 neutrons is used in many smoke alarms. (a) How many electrons does an atom of americium have? (b) What is the isotope's mass number A? (c) Write its nuclear symbol. 13. Consider the following nuclear symbols. How many protons, neutrons, and electrons does each element have? What elements do R, T, and X represent? (a) AR 14. Consider the following nuclear symbols. How many protons, neutrons, of (c) X (b) T and electrons does each element have? What elements do A, L, and Z represent? (a) JA 15. Nuclei with the same mass number but different atomic numbers are called isobars. Consider Ca-40, Ca-41, K-41 and Ar-41. (a) Which of these are isobars? Which are isotopes? (c) Z (b) {L ce ts (b) What do Ca-40 and Ca-41 have in common? (c) Correct the statement (if it is incorrect): Atoms of Ca-41, K-41, and ut Ar-41 have the same number of neutrons. 16. See the definition for isobars in Question 15. Consider boron-12, and write the nuclear symbol for (a) an isobar of boron-12 with atomic number 6. (b) a nucleus with 4 protons and 8 neutrons. Is this nucleus an isotope or an isobar of boron-12? (c) a nucleus with 5 protons and 6 neutrons. Is this nucleus an isotope or an isobar of boron-12? ts e- he Atomic Masses and Isotopic Abundances is 17. Calculate the mass ratio of a bromine atom to an atom of (b) calcium (c) helium (a) neon -o- 18. Arrange the following in order of increasing mass. (a) a sodium ion (c) a sulfur (Sg) molecule 19. Cerium is the most abundant rare earth metal. Pure cerium ignites when scratched by even a soft object. It has four known isotopes: "Ce (atomic mass = 135.907 amu), 198Ce (atomic mass 139.905 amu), and 14Ce (atomic mass = fairly abundant. Which is the more abundant isotope? 20. Consider the three stable isotopes of oxygen with their respective ur- (b) a selenium atom (d) a scandium atom n- 137.905 amu), Ce (atomic mass = 141.909 amu). Ce-140 and Ce-142 are cite atomic masses: O-16 (15.9949 amu), O-17 (16.9993 amu), O-18 (17.9992 amu). Which is the most abundant? Notifications Inbox Dashboard Calendar To Do