Answer: 20 mg Te-99 remains after 12 hours.
Explanation: N(t) = N(0)*(1/2)^(t/t1/2)
N(t) = (80 mg)*(0.5)^(12/6)
N(t) = 20 mg remains after 12 hours
A substance that cannot be broken down into even by chemical means is called an element. About 90 elements on the Periodic Table can be found naturally on Earth. Three of the most common ones are aluminium, silicon and oxygen.
Sorry I couldn't give you a more specific answer as your question wasn't multiple choice.
The correct answer is Kinetic energy
