Half life Not the video game (Sec 10.4 pg 290 – 296)

Half-life is the average length of time it takes for half of the parent nuclei in a sample to undergo radioactive decay.

Half-life is different for different isotopes, but is constant for an individual isotope.

The number of decays per second is known as the activity level and it is measured in Becquerels (# of decays per second).

Half-life is often used to date materials (e. g Half-life is often used to date materials (e.g. carbon-14 can be used to date things that were alive; Fig.9 p.294).

How do we know the half-life of atoms Half lives are independent of the original amounts. You can measure them by taking a small amount of material, estimating how many atoms there are in total, and then counting the number of atoms that decay on average every second. This can be used to calculate the half life using the mathematics of exponentials.

We find something that contains an isotope that had a known initial quantity and calculate how old the object must be. This is called radioactive dating.

There are a few different ways to calculate the amount of parent nuclei remaining in a sample. You may develop your own way, but here’s a couple methods from the text:

You can use half-life to calculate rate of decay OR the amount of original sample present (see both sample problems in text pg 292-3).

Radioactive decay involves a parent nucleus producing a daughter nucleus. However, the daughter nucleus itself is radioactive, and thus could be considered a parent nucleus capable of producing another generation.

When radioactive nuclei form a chain, it’s called a decay series (Fig When radioactive nuclei form a chain, it’s called a decay series (Fig.8 and Table 3 p.294)

Watch Video 1 Watch Video 2 Homework 296 Pg 2-5