1. Half – Life All radioisotopes have a half life. The half is of any given radioisotope is the amount of time required for one half (50%) of the sample to decay

2. The equation # of half lives Total Time elapse (HOW LONG) Half – Life (can be found in table N) 80g40g20g10g 1 2 3 The sample above went through 3 half lives, meaning it was cut in half 3 times. It is now 1/8 it’s original amount ½ ½ ½ = 1/8

3. Sample Problem 288 Ac has a half life of 6.13 hours. How much of a 60 mg sample would remain after 24.52 hours? # of half lives 24.52 HR 6.13 HR 60g30g15g7.5g 3.75g 1 2 34 3.5 g would remain 4 So, 60 is going to get cut in ½ 4 times