Question

One gram of Radium, with atomic weight 226, emits 4 × 10¹⁰ particles per second. The half-life of Radium is

Answer 1

226 grams of radium is considered as 1 mole
so 1 gram is considered as 1/226 moles

and weknow that 1 mole of a substance contains avagrodo number of particles
so 1/226 moles contains 1/226*avagardo number of particles

and so in a half life time the susbstance become 50% of its initial amount
So 1/226 moles becomes 1/452 moles

so you have got to multiply 1/452 with avagrado’s number and divide it by 4*10^10 andd you get the half life period

= 0.0033 * 10^13
=3.3 * 10^10