Strontium-90 is radioactive and has a half life of 28.8 years. How much of a 2.90mg sample would be left after 137. years? Round your answer to 2 significant digits. Also, be sure your answer has a unit symbol.

Examine the false statement. compounds are the smallest unit of an element that occur most commonly in nature. select the rewording of the statement that is true. a: atoms are the smallest unit of an element that commonly occur in nature. b: molecules are the smallest unit of an element or compound that commonly occur in nature. c: molecules are the smallest unit of a compound that occur on the periodic table. d: compounds are the smallest unit of an element that occur on the periodic table