Download SCIENCE 10: (7.1) ATOMIC THEORY, ISOTOPES

SCIENCE 10: (7.1) ATOMIC THEORY, ISOTOPES AND RADIOACTIVE DECAY
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(Textbook Reference pp. 286-301 in BC Science 10)

Natural background radiation: __________________________
_______________________________________________
_______________________________________________
_______________________________________________
 It has the ability to interact with an atom and turn it
into an _______

Radiation: __________________________________________
_______________________________________________
 When atoms lose high-energy particles and waves, ions or
even new atoms can be formed.
 High-energy waves and particles are called radiation
when they leave the atom.

Radioactivity: _______________________________________
_______________________________________________
_______________________________________________

Being exposed to radioactive materials can be beneficial or
harmful.
 Beneficial: __________________________________
 Harmful:____________________________________
ISOTOPES AND MASS NUMBER

Isotopes:__________________________________________
_______________________________________________
_______________________________________________.
 Remember that an atom of an element will have the same
number of protons and electrons (___________________)
 Not all atoms of an element have the same number of
neutrons (_______________).
 Remember the mass number tells you the total number of
__________ and _______________ in an isotope.
 Isotopes of an element have the same __________
and same ___________ _________________
 Mass number = ______________ + _____________
 Atomic mass = ____________________________
_____________________________________.
REPRESENTING ISOTOPES
http://www.colorado.edu/physics/2000/isotopes/index.html

Isotopes are written using standard atomic notation.

The standard atomic symbol (or nuclear symbol) for the following
isotopes of potassium would be:
o Potassium-39
o Potassium-40
o Potassium-41
In nature, most elements are found as a mixture of isotopes.
http://www.chem4kids.com/files/atom_isotopes.html
Complete the Practice Problems on p. 291
RADIOACTIVE DECAY

Radioactive decay: ___________________________________
_______________________________________________
_______________________________________________

Radioactive atoms release energy until they become __________,
often as different atoms.
 Ex. Uranium -238 undergoes 14 different radioactive decay
steps before forming stable lead-206.

An element may have only certain isotopes that are radioactive.
 Isotopes that are capable of radioactive decay are called
_______________________.
THREE TYPES OF RADIATION
 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.

ALPHA RADIATION

Alpha radiation is a stream of ________ particles.
 They are _______________ charged, and are the
_______ massive of the radiation types.
 Alpha particles are essentially the same as __________
atoms.
 Alpha particles are represented by the symbols:

Because it has two protons, it has a charge of ___

The release of alpha particles is called
__________ ____________.
 Alpha particles are _______ and penetrate materials
much _______ than the other forms of radiation. A
sheet of __________ will stop an alpha particle.
Example:
***Note: The equation is balanced! (The sum of the atomic numbers and the sum of
the mass numbers are equal on both sides of the arrow. Also the product
nucleus has an atomic number that is lower by two and a mass number that is
lower by four due to the alpha particle)
Complete the Practice Problems on p. 295
BETA RADIATION

A beta particle is an _____________ and is _______________
charged.
 Beta particles are represented by the symbols:

Electrons are very tiny, so beta particles are
assigned a mass of ____.

Since there is only an electron, a beta particle has
a charge of _____.
 Beta decay occurs when a ______________ changes
into a ___________+ an _______________.

The proton stays in the nucleus, and the electron is
________________.

It takes a thin sheet of ___________________
to stop a beta particle.
Example:
***Note: The equation is balanced! (The sum of the atomic numbers and the sum of
the mass numbers are equal on both sides of the arrow. Also the product
nucleus has an atomic number that is greater, making it an atom of the next
higher element and a mass number that equal to the reactant because the beta
particle emitted was an electron)
Complete the Practice Problems on p. 296
GAMMA RADIATION

Gamma radiation is a _______ of high-energy, short-wavelength
radiation.
 Gamma radiation has ______ charge and _____ mass,
and is represented by the symbol
 Gamma radiation is the _____________-energy form of
electromagnetic radiation.

It takes thick blocks of _______ or
___________ to stop gamma rays.
 Gamma decay results from __________ being released
from a high-energy nucleus.
 Often, other kinds of radioactive decay will also release
gamma radiation.

Uranium-238 decays into an alpha particle and also
releases gamma rays.
Example:
***Note: The equation is balanced! (The sum of the atomic numbers and the sum of
the mass numbers are equal on both sides of the arrow. Also the product
nucleus has an atomic number and a mass number that are equal to the reactant
because gamma decay involves energy, not particles.)
SUMMARY:
Type
ALPHA
BETA
GAMMA
RADIATION
RADIATION
RADIATION
ALPHA DECAY
BETA DECAY
GAMMA DECAY
Symbol
Particle or Ray
Description of
Radiation
Charge
Relative mass
Chemical symbol
Can be stopped
by:
Particle emitted
Change in mass of
starting nucleus.
Change in atomic
number of
starting nucleus.
 Remember the following rules when you write a nuclear equation:
1. _____________________________________________________
2. _____________________________________________________
More Practice: Complete p. 301 #4, 7, 11-13