The half-life of radium is 1620  years and its atomic weight is 226. The number of atoms that will decay from its 1 g sample per second will be:

According to avogadro's hypothesis.N0=6.02 x 1023226=2.66 x 1021Half-life=T=0.693λ=1620 years∴λ=0.69311620 x 3.16 x 107        =1.35 x 10-11sec-1Because half-life is very much large as compared to its time interval, henceN=N0 Now dNdt=λN0 or dN=λN0dt           =(1.35 x 10-11)(2.66 x 1021) x 1           =3.61 x 1010