What is the half-life of a radioisotope if a 20 g sample becomes 5 g after 2 days?

Ahypothesis must be testable and falsifiable to be considered scientific a. trueb. false

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.

Who determined the nature of chemical bonds?