Multiple choice The isotope used for determining the age of water is chlorine-36 magnesium-27 lead-210 beta 22 potassium-40 Reveal answer Fill a bubble to check yourself A Correct answer Explanation Chlorine-36 emitts beta particles.Its half life is 301,000 years.It is used in the measurement of sources of chloride and determining the age of water up to about 2 million years old.It is a naturally occurring radioisotope .