Nuclear Decay and Half-Life

What is Half-life?

• The amount of time it takes for some of the nuclei in a sample of the isotope to decay
• The amount of time it takes for half the electrons in a sample of the isotope to decay
• The amount of time it takes for half the nuclei in a sample of the isotope to decay
• the amount of time it takes to double the nuclei in a sample of the isotope to decay

The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

• 100.0g
• 50.0g
• 12.5g
• 8.5g

The mass number of Neptunium (Np) is _____.

The atomic number of Neptunium (Np) is _____.

The atomic number of Actinium (Ac) is _____.

Solve this equation for alpha decay.
₈₅²⁰⁹At = ___ + ₂⁴He

• ₈₃²⁰⁵Bi
• ₈₆²⁰⁹Rn
• ₈₁²⁰⁷Tl
• ₈₅²⁰⁸At

Solve this equation for beta decay.
₆¹⁴C = ___ + _-1⁰e

• ₄¹⁰Be
• ₇¹⁴N
• ₂¹⁰He
• ₆¹³C

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g
• 2.5g
• 25g
• 80g

What percent of carbon-14 would be left after 5730 years?

• 100%
• 75%
• 50%
• 25%

What is the half-life of iodine-131?

• 32 days
• 8 days
• 16 days
• 24 days