An α - particle changes into a Helium atom. In the course of one year the volume of Helium collected from a sample of Radium was found to be 1.12×10–2mL at STP. The number of α - particles emitted by the sample of Radium in the same time is

Ra - isotope α-emission He gasWe know that α-particles are double positively charged Helium nuclei.α-rays change to Helium gas.Volume of He gas = 1.12×10-2 ml at STP22400cc of the He at STP contain 6.023×1023 He-atoms1.12×10-2 cc of He at STP contain 'X' atoms   Number of α-particles emitted = 3×1017