Nov. 20 – Radiation and Radioactive Decay

Today we discussed radiation.  Here are the notes:

Marie Curie was one of the first people to study radiation.

Radiation

Review: 

   proton - positively charged particle

   neutron - neutral particle, same mass as proton.

   electrons - negatively charged, 1000 times lighter

Isotopes

    - isotopes are two or more atoms that have the same number of protons, but different number of neutrons.

Isotopes of lithium.

Notation: 

Use this notation for each element, mass number and proton number.

Example: This is how you would write krypton with a mass of 78. 

How many protons and neutrons does it have?

Answer: Protons = 36, Neutrons = 78 – 36 = 42

What is radiation?

  - radiation is high energy particles or high energy electromagnetic waves

Small amounts of radiation can be used to diagnose diseases such as in a PET scan.

Here's what a chunk of radioactive uranium looks like.

Nuclear Radiation

   - radiation emitted from an unstable nucleus.

   - the original nucleus is the “parent”

   - the products are called “daughters”

   - there are three types: alpha, beta, and gamma

Alpha Decay

   - an alpha particle consists of 2 protons and 2 neutrons (same as He nucleus)

   - relatively large, easily stopped

   - can penetrate a few cells into the body

Ex) Write the equation for Cu-64 undergoing alpha-decay.

Beta Decay

   - A neutron decays into a proton, electron and anti-neutrino

   - A beta particle is a high energy electron

   - lighter and faster than alpha particles

   - can be stopped by thin metal or plastic

Ex) Write the equation for Oxygen-19 undergoing beta-decay.

Gamma Decay

   - A nucleus in an excited state loses energy and emits a photon

   - A gamma particle is a high energy photon

Summary

Homework

• Please catch up on any homework you have not completed yet.