Decays by alpha emission to give
)If unshaded spheres represent
Atoms and shaded spheres represent
Atoms,how many half-lives have passed in the following example?

Question

Decays by alpha emission to give 
)If unshaded spheres represent 
Atoms and shaded spheres represent 
Atoms,how many half-lives have passed in the following example?

Quizplus · Accepted Answer

The decay from 11ea7a38_c94e_c002_aa4c_1f24c3f65695_TB4939_00 to 11ea7a38_c94e_e713_aa4c_f3178d99a1c2_TB4939_11 involves alpha emission, which means the atom loses two protons and two neutrons. This changes the identity of the atom, so we cannot use it for the subsequent calculations. Instead, we consider the unshaded spheres, which represent 11ea7a38_c94e_e714_aa4c_ab03d84f377d_TB4939_11. We can see that two unshaded spheres have turned into shaded spheres, meaning two half-lives have passed. Therefore, the answer is B.

Decays by Alpha Emission to Give