8 g of Cu⁶⁶ undergoes radioactive decay and after 15 minutes only 1 g remains. The half-life, in minutes, is then

• 15 ln (2) / ln(8)

• 15 ln (8) / ln (2)

• 15/8

• 8/15

72.

For a light nuclei, which of the following relation between the atomic number (Z) and mass number (A) is valid ?

• A = Z/2

• Z = A

• Z = A/2

• Z = A²