Radium-228 is a radioactive isotope which decays by α-emission to an isotope of radon (Rn). Two further α-emissions give in turn isotopes of polonium (Po) and lead (Pb). The lead isotope normally decays by β-emission to an isotope of bismuth (Bi). There is significant γ-emission with the decays of the radium and the lead.
The atomic number of radium (Ra) is 88.
(a) Write the nuclear equation of the decay of radium (Ra) to radon (Rn).
(b) Fill up the table below showing the nucleon (mass) numbers, proton (atomic) numbers and neutron numbers of the elements described above.
(c) The decay of 16 g of lead (Pb) to 14 g bismuth (Bi) takes 66.9 years. Find the half life of the radioactive of lead (Pb).
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Answer:
(a)
(b)
(c) Since mass num of Pb is same as mass num of Bi, 16 g of Pb will decay to 16 g of Bi eventually.
Since there is 14 g of Bi, it means 2 g of Pb is left.
16 g Pb -> 8g Pb -> 4g Pb -> 2g Pb
Hence, 3 half lives = 66.9 years
Half-life = 22.3 years
