Q-1: Each element of the period table is defined by the number of protons in the nucleus of the atom, which assigns the atomic number of the element. The mass number (amu = atomic mass units) of an atom is the sum of the protons (each proton = 1 amu) and the number of neutrons (each neutron = 1 amu).
Based on the above information, Th-232 (Thorium with mass = 232 amu, atomic number 90) would have ________ protons and _______ neutrons.
Q-2: Three main types of decay processes involve:
Alpha decay: nucleus spontaneously emits anα (alpha) particle, same as Helium nuclei, which is 2 p+ and 2 n. Result: atomic number decreases by 2 (lost 2 p+); atomic mass decreases by 4 (lost 2 p+ and 2n = 4 amu)
Beta decay: neutron in nucleus spontaneously emits a β (beta) particle, which is essentially an electron trapped in a neutron. The neutron, therefore, turns itself into a proton. Result: atomic number increases by 1 (gained 1 p+); atomic mass stays same.
Beta or electron capture: : proton in nucleus captures a β (beta) particle which is essentially an electron that can become part of a neutron. The proton, therefore, turns itself into a neutron. Result: atomic number decreases by 1 (lost 1 p+); atomic mass stays same.For example: Po-206 (atomic no = 84) with α decay makes Pb-202 (atomic no = 82)
Based on the above information, complete the following radioactive transformations (You may need to refer to a periodic table):
Bi-206 = ________ + β (Note: β on the product side means decay from Bi)
Tl-202 + β = ________ (Note:β on the reactant side means nucleus captured a beta particle)
Pu-244 = _______ + 2α + 2β (Note: there are two types of particle decaying twice).
Q-3: Mercury is a well-known element with known toxicity and is used to extract gold from rock ores since very early times. In fact, the Spanish were known to extensively dig out large mercury deposits for gold extraction over 300 years ago. If you take a look at the periodic table, you will find that platinum, gold and mercury sit side by side. While platinum is indicated as Pt in the periodic table, named after the Spanish word "platina" meaning "little silver", the symbol for Gold is _______ an abbreviation for Aurum and, that for mercury is __________ an abbreviation for the word _____ (search the web to find this).
Mercury is one of the few elements that is in liquid form on the Earth's surface conditions, hence was/is used in thermometers and barometers. Research and comment on where would one find mercury deposits in nature - i.e. will you be looking in hot volcanoes, or is it just a random luck?
Q-4: Following are some Parent - Daughter isotope pairs with their half-life (T1/2):
U-238 going to Pb-206 (T1/2 = 4.5 x 109 years)
U-235 going to Pb-207 (T1/2 = 0.7 x 109 years)
C-14 going to N-14 (T1/2 = 5700 years)
If the C-14: N-14 ratio in a shell in a sandstone was found to be 1 : 3, how old is the shell? ____________________ Years.
If the U-235: Pb-207 ratio in a rock from Massachussets was determined to be 1 : 15, how old is the rock? ____________years
If the U-238: Pb-206 ratio in a crystal of zircon found in sandstone was determined to be 1: 7, what radiometric age will this give for the zircon? _____________ Years. Does this determined age realistic? If no, why not? If yes, how? (Explain briefly).