 Radioactivity (Radiation) is the release of high-energy particles and rays of energy from a substance as a resultof changes in the nuclei of its atoms. › When atoms radiate, another element can be formed. › We call it radiation only when the energy comes from the nucleus of the atom

 Natural radiation exists all around us, from: radioactive substances in the Earth´s crust to cosmiv rays from outer space that bombard Earth. Trace amounts from these sources can be found in our food and water.

 Being exposed to radioactive materials can be beneficial or harmful. Beneficial (GOOD) Radiation Exposure Harmful Radiation Exposure -Medical imaging (iron-59) -Cancer treatment: radiation therapy -X-rays -Electricity generation -Beta and Gamma radiatio can penetrate your skin and damage your cells. -High-energy particles and waves damage DNA in our cells.

Increasing Frequency Decreasing Wavelength The the higher the frequencyof the radiation (i.e.the shorter the wavelength)= the more harmful the radiation is for you!

How Radiation Happens: 1. An atom has an unstable nucleus 2. The unstable nucleus splits apart 3. Energy is released (we say ¨a nucleur reaction¨occurs) 4. The atom will contunue to radiate until it becomes stable (often ending up as different atoms)

An element may only have certain isotopes that are radioactive. These are called radioisotopes.

 Isotopes are different types if the same element, that have a different number of neutrons in the nucleus.  Isotopes have the same number of protons and electrons-so, they have the same atomic number and symbol BUT…  Different number of neutrons and therefore different mass number  Mass number refers to the #protons (atomic number) + #neutrons in an isotope

 Isotopes are written by: 1. Putting the mass number at the top left. 2. Putting the atomic numberat the bottom left. Potassium has three isotopes:

When atoms are unstable, they break apart to become new, more stable atoms, and release radiation. There are three types that can be released: 1.Alpha 2.Beta 3.Gamma

 Alpha radiation is a tream of alpha (helium) particles › Charge: +2 (2 protons) › Alpha particles are the same as a helium atom. So we represent radiation:

 The release of alpha particles is called alpha radiation.  Alpha particles are slow and not very harmful. A sheet of paper will stop an alpha particle.

 Beta radiation is a stream of beta (electron) particles,. › Charge: -1 (1 electron) › We represent radiation as: › Beta particles are faster and more harmful than alpha. A sheet of metal foil (aluminum foil) will stop a beta particle.

 Gamma radiation is a ray of high energy. › No charge 0) and no mass (almost no mass). › Gamma radiation is the highest energy form of the electormagnetic radiation (most dangerous)

 Gamma decay results from energy being released from a high-energy nucleus. It is shown by:  It takes thick blocks of lead or concrete to stop gamma rays.

 Gamma rays accompany the alpha decay og uranium-238.

* Means the nickle nucleus has extra energy!