# What is half-life?

##### 1 Answer

Half-life (

In nuclear chemistry, the half-life is the time needed for half of the radioactive atoms to decay.

For example, carbon-14 has a half-life of 5730 yr.

If we start with 10.0 g of carbon-14, the amount remaining after 5730 yr (1 half-life) will be 10.0 g × ½ = 5.00 g.

After 2 half-lives, the amount remaining will have decreased to 2.50 g.

10.0 g × ½ × ½ = 10.0 g ×

After 3 half-lives, the amount remaining will have decreased to 1.25 g.

10.0 g × ½ × ½ × ½ = 10.0 g ×

After 4 half-lives, the amount remaining will have decreased to 0.625 g.

The general formula to calculate the amount remaining after a given number

Thus, after four half-lives, the formula gives