what do you notice aboutt the location on the periodic table of the elements that represent the low points

Your question is not clear but if you can explain yourself i would be glad to .  just trying to : ))

Hello.the answer is  hydrosphere, geosphere, and biosphere  have a nice day

Pretty sure it's d. heterogeneous is separated by physical properties. 

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.