Question

3. If you started with a sample of 600 radioactive nuclei, how many would

remain undecayed after three half-lives?

Answer 1

`\boxed {\boxed {\sf 75 \ radioactive \ nuclei}}`

Step-by-step explanation:

Radioactive decay occurs in unstable atom nuclei. The ratio of protons to neutrons is off, causing the instability. The nuclei release particles and radiation to change into different atoms.

The half-life is the time it takes for half of the nuclei to decay. We don't know the half-life of the sample, but we know it undergoes 3 half-lives. Therefore, the number of radioactive nuclei halves every time the sample undergoes a half-life.

We can divide the number of nuclei in half 3 times to find the amount left after 3 half-lives.

• 1st half-life: 600/2 = 300
• 2nd half-life: 300/2 = 150
• 3rd half-life: 150/2= 75

After 3 half-lives, 75 radioactive nuclei remain undecayed.