Question

THE HALF LIFE OF A RADIOACTIVE ELEMENT IS 10 HOURS. HOW MUCH WILL BE LEFT AFTER 4 HOURS IN 1 GRAM ATOM SAMPLE ?

Answer 1

Half   life   period of a reaction is also defined as the time taken for the concentration of a reactant to reduce to one half of its initial concentration. Radioactive decay is a first order reaction.

For a first order reaction, 4/10 => 2/5 or => 0.4 half-lives, After 0.4 half lives, the amount would be left => (1/2)^0.,  ((1/2)^0.4)*1 gm =>  (1/2)^0.4 gms.

Answer 2

$\huge \tt {( \frac{1}{2} )}^{0.4} \: \: \: grams$