Is it Chemistry or Physics?

Classical Mechanics Level 2

There are 2.68 $\times$ 10 $^{18}$ atoms in 1 mg of radium , whose half-life is 1620 years. How many radium atoms will decay from 1 mg pure radium in 3240 years?

3\times10^8

2.01 \times 10^{18}

3\times10^{17}

2.02\times10^{18}

1 solution

Chew-Seong Cheong
May 28, 2016

From 1 mg or $2.68 \times 10^{18}$ atoms of radium, half ( $\frac{1}{2}$ ) of it will decay in a half-life of 1620 years. In 3240 years or another half-life half of the remaining half or ( $\frac{1}{2}\times \frac{1}{2} = \frac{1}{4}$ ) will decay, therefore a total of $\frac{3}{4} \times 2.68 \times 10^{18} = \boxed{2.01 \times 10^{18}}$ will decay away.

Is it Chemistry or Physics?

1 solution

0 pending reports