This radioactive element has a mass of 16 g.
After 10 minutes, half of the mass of the element will have decayed. This means that after 10 minutes, there will be 8 g of the element remaining.
After another 10 minutes (20 minutes total), half of the remaining 8 g will have decayed, leaving 4 g of the element.
After another 10 minutes (30 minutes total), half of the remaining 4 g will have decayed, leaving 2 g of the element.
After another 10 minutes (40 minutes total), half of the remaining 2 g will have decayed, leaving 1 g of the element.
After another 10 minutes (50 minutes total), half of the remaining 1 g will have decayed, leaving 0.5 g of the element.
After another 10 minutes (60 minutes total), half of the remaining 0.5 g will have decayed, leaving 0.25 g of the element.
And so on, with the mass continuing to decrease by half every 10 minutes.