Cs is more reactive than Sr
<span>1.23x10^24 atoms/6.022x10^23 atom/mol = 2.04 mol H20 </span>
Usually, they aren't found in the same place because fossils are already very rare. For every 1 billion humans, there would only be one fossil. So the odds would be very slim for them both to be found in the same place.
Hope I helped!
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~ Zoe