How long does it take for 87.5 % of each isotope to decay? (The isotopes are below)
Krypton-73= 27 seconds
Krypton-74= 11.5 minutes
Krypton-76= 14.8 hours
Krypton-81= 2.1 x 10^5 years

Kr-73 = 23.625 sec

Kr-74 = 10.0625 minutes (603.75 seconds)

Kr-76 = 12.95 hours (777 minutes)

Kr-81 = 1.8375 * 10^6 years

Explanation:

What you do is multiply each of those amounts by 7/8.

27 * 7/8 = 189/8 = 23.625

23/2 * 7/8 = 161/16 = 10.0625

74/5 * 7/8 = 518/40 = 259/20 = 12.95

210000 * 7/8 = 1470000/8 = 183750 = 1.8375 * 10^6

each  column  of the  table  is called a group. elements in a group share similar properties. groups are  read  from  top  to  bottom. metal. metalloid. nonmetal. solid. liquid. gas. fe. hg. o.  2. 3. 4. 5. 6. 7. 8. 9.  2. beryllium. 9.012. 4.  sodium. 22.990.  11. 3.  magnesium. 24.305.  12.  potassium. 39.098.  19. 4.  calcium. 40.078.  20. i guess  i  

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