7.1 Atomic Theory and Radioactive Decay

7.1 Atomic Theory and Radioactive Decay

Natural background radiation exists all around us.

______is the release of high energy particles or waves.

-When atoms lose high energy particles and waves, ______ can be formed.

–Radiation is useful (medical scans & cancer treatment) but it damages DNA in cells.

The Electromagnetic Spectrum

Isotopes

are different atoms of the same element, with a different number of ______in the nucleus.

–changing the # of ______changes the ______number

Remember: mass # = ______

–isotopes still have the same ______

Atomic Mass (the decimal #’s)

Atomic mass = ______.

Representing Isotopes

Isotopes are written using standard atomic notation.

–Chemical symbol + atomic number + mass number.

–Potassium has three isotopes,

Radioactive Decay

Can result in new ______forming.

–Radioactivity results from having an ______.

–Radioactive decay = when nuclei break apart + release ______from the nucleus as ______.

Radioactive decay continues until a ______element forms.
An element may have only certain isotopes that are radioactive called ______

Uranium goes through many decay steps before it becomes stable.

Rutherford identified three types of radiation using an electric field.

–Positive ______were attracted to the negative plate.

–Negative ______were attracted to the positive plate.

–Neutral ______did not move towards any plate.

A) Alpha Radiation:

is a stream of alpha particles, (shown as )

–______

–the most massive of the 3 types and are the equal toa Helium nucleus.

–Alpha particles are represented by the symbols:

2 protons and 2 neutrons make a mass number of 4
it has a charge of 2+ because of the protons

Alpha particles are ______and penetrate materials much less than the other forms of radiation. A sheet of paper will stop an alpha particle.

The release of alpha particles is called ______.

Example: the alpha decay of Radium – 226



B) Beta Radiation:

A Beta particle, ______ is a ______.

–______charged, and are ______massive than alpha particles.

–Beta particles are represented by the symbols :

electrons are very tiny, so beta particles are assigned a mass of __.
one electron gives a beta particle has a charge of ______.

Beta decay occurs when a neutron changes into a ______+ an ______.
The proton stays in the ______, and the electron is ______.

Example: The beta decay of iodine - 131

It takes a thin sheet of aluminum foil to stop a beta particle.

C) Gamma Radiation:

Gamma radiation, ___, is a ray of ______energy, short-wavelength radiation.

–has ____ charge and _____ mass.

–is the ______energy form of electromagnetic radiation.

–It takes thick blocks of lead or concrete to stop gamma rays.

–Gamma decay results from ______being released from a high-energy ______.

Often, other kinds of radioactive decay will also release gamma radiation.

–Uranium-238 decays into an alpha particle and also releases gamma rays.

Nuclear Equations:

are written like chemical equations, but represent ______in the ______of atoms.

–Chemical equations represent changes in the position of atoms, not changes to the atoms themselves.

Remember:

–The sum of the ______on each side of the equation should equal.