The half-life of F-20 is 11.4 seconds When there are 200 atoms of F-20 in a sample a scientist starts a stopwatch The scientist stops the stopwatch at 34.2 seconds there are atoms of F-20 re?

Answer 1

Atomic decay is a random phenomenon whose distribution is exponential (generally). Thus if the average lifetime is t0 and you wait a time t, the probability that a single atom decay is

p=(1-exp(-t/t0))

Thus if you have N atoms, the average number of atoms that decay in the tine t is

<N> = N0 (1-exp(-t/t0))

where N0 is the initial number.

naturally in a specific experiment the real number of atoms that decay in a time t will not be exactly <N>, this is only the average number over a potentially infinite number of experiments.

However, greater N0, more likely the number of atoms observed in a specific experiment will be near to <N>.

In your case <N>=188.1 and the expected deviation is of the order of 13, thus the result could fluctuates with high probability between 200 (that is all decay) and 162 (2 sigma point).

Answer 2

At start there 200 atoms

At 11.4 secs there are 100 atoms

At 22.8 secs there are 50 atoms

At 34.2 secs there are 25 atoms.

Half life - atoms/ 2^(n-1)

half life = 200 / 2(^3)

half life = 200 /8

Half Life = 25 atoms.

Answer 3

there are 25

Answer 4

Half from half is quarter.

Answer 5

50