Uranium-234 is used to make dental crowns appear brighter. The alpha decay of Ur

Question

Uranium-234 is used to make dental crowns appear brighter. The alpha decay of Uranium-234 produce what isotope? The electron capture of Strontium-85 can be used by physicians to study bone formation. Write a balanced nuclear equation for reaction. The half-life of Polonium-218 is 3 min. If you start with 20 g how long will it be before 1 g remains? An unknown radioisotope exhibits 8540 decays per second. After 350 minutes, the number of decays has decreased to 1250 per second. What is the half-life?

Explanation / Answer

1) thorium-230
Well in alpha decay the nucleus will lose 2 protons and 2 neutrons. So its new atomic mass will be 230 and its proton number 90. This is an isotope of the element THORIUM.

2) -1-e-0 + 38-Sr-85 ---> 37-Rb-85
That's a negative one for the "atomic number" on the electron.

3) A = A0 e^-(0.693t/T) A0=20 gm, T=3 mins, A=1gm
1 = 20 e^-(0.693t/3)
1/20 = e^-(0.693t/3)
-0.693t/3 = ln(1/20)
t = -3ln(1/20)/0.693
t= 12.96 minutes

4) A fraction of 1250/8540 =1/6.832 = 1/2^2.772 is left.
Therefore 350.0 minutes equals 2.772 half lives.
So the half life is 350.0/2.772 = 126.2 minutes

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