Question

Suppose there are 100,000 atoms of a radioactive substance that has a ½ life of 10 minutes. How many atoms will remain after 40 minutes:

a. 2,500
b. 10,000
c. 12,500
d. 50,000

Show calculation

Answer 1

c. 12,500

Step-by-step explanation:

Original number of atoms = 100,000 atoms

Half- life = 10min

Unknown:

The number of atoms that will remain after 10min = ?

Solution:

The half - life is the time taken for half of a radioactive substance to decay by half.

Time taken Number of atom half life

10min 100000 _

20min 50000 1

30min 25000 2

40min 12500 3