If a 500.0 g sample of technetium-99 decays to 62.5 g of technetium-99 remaining in 639,000 years, what is the half-life of technetium-99?

It takes 2113000 years for a 500.0 g sample of technetium-99 decays to 62.5 g.    

Half Life:

It is the time in radioactive substance remains half of its initial concentration.

The initial amount of radioactive Technetium-99 present in the sample is  

= 500 g  

After 1 half life the remaining mass of the Technetium-99 is  

= 250 g  

After 2 half life the remaining mass of the Technetium-99  is  

= 125 g  

After 3 half life the remaining mass of the Technetium-99 is  

m = 62.5 g  

So after 3 half life the remaining Technetium-99 is 62.5 g.  

Thus,

Therefore, it takes 2113000 years for a 500.0 g sample of technetium-99 decays to 62.5 g.

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Half life of the sample is given as

Explanation:

As we know that radiactive substance becomes half in one half life time period

here we know that initial amount of radioactive substance present in the sample is

m = 500 g

After 1 half life the remaining mass of the sample is

m = 250 g

After 2 half life the remaining mass of the sample is

m = 125 g

After 3 half life the remaining mass of the sample is

m = 62.5 g

So the given time interval is equivalent to 3 half life

so we have

hèllo, sorry i really need some more points so if you need this qustion answered than retype it

i had this question and the answer was 3.15 miles.

martina travels from school to her mom's office. from there, she walks to school. after school, she walks to the library and then to a friends house before finally ending back at home. find martina's total distance traveled.

a) 0 miles  

b) 0.4 miles  

c) 1 mile  

d) 3.15 miles