The half-life of radium-226 is 1620 years. how much of one gram of radium-226 will remain unchanged after four half-lives?
a) 0.125 g
b) 0.50 g
c) 0.0625 g
d) 0.25 g

0.0625 g

Step-by-step explanation:

Given : The half-life of radium-226 is 1620 years.

Formula of half life:

So. = initial amount

P(t)= mass of radioactive material at time interval (t)

1 half life = 1620 years

4 half lives = 4 * 1620

So, t = 4 * 1620

Substituting the values :

Hence  0.0625 g of one gram of radium-226 will remain unchanged after four half-lives

Option C is correct.