Transcript 10 - Lighthouse Christian Academy

10.1
Radioactivity and its History
• Scientists in the late 1800s determined that there were
different types of radiation in addition to visible light.
VOCABULARY
radioactivity
• Some types of radiation have mass, some do not.
• Some types of radiation are electrically positive, some
are negative or neutral.
• Cathode rays were found to be made up of
electrons by Sir J.J. Thomson in 1897.
• Cathode ray tubes were the basis of the television
until LCD and plasma screens.
• X-rays were discovered by Wilhelm Röntgen in 1895
and were found to be part of the electromagnetic spectrum.
• Henri Becquerel and Marie and Pierre Curie were the pioneer
scientists of radioactive elements.
• Marie Curie coined the term radioactivity for the spontaneous
emission of radiation from the nucleus of an atom.
10.2
Radioactivity and the Nucleus
• All atoms are made of subatomic particles.
• All atoms of an element have the same chemical
properties, although the atoms of an element can have
different masses.
• Atoms of the same element with different masses are
called isotopes of that element.
• An isotope of an element has the same atomic number,
but a different mass number.
• This means that they have the same number of protons,
but a different number of neutrons.
VOCABULARY
nucleus
proton
neutrons
isotopes
10.2
Radioactivity and the Nucleus
• Isotopes can be written in standard atomic notation.
• For example: uranium-238
238
92
U
VOCABULARY
nucleus
proton
neutrons
isotopes
carbon-12
12
6
C
10.3
Radioactive Decay
• An unstable nucleus that emits radiation is
undergoing radioactive decay.
VOCABULARY
radioactive decay
parent nucleus
• Transmutation changes a parent nucleus into a
daughter nucleus.
daughter nucleus
• Radioactive atoms emit radiation of three different
types:
beta particle
1. alpha radiation
2. beta radiation
3. gamma radiation
• Alpha, beta, and gamma radiation have
different properties of mass, charge,
penetrating ability, and reaction to electric
and magnetic charges.
alpha particle
gamma ray
10.4
Half-Life
• The rate of radioactive decay of a sample is not
affected by physical or chemical changes such as
temperature, pressure, or age of the sample.
• The rate of decay of a radioactive sample is predictable.
VOCABULARY
half-life
decay series
10.4
Half-Life
• The average length of time for half of the parent nuclei
in a sample to decay is called the half-life.
• It is a constant number for a given isotope.
• The half-life of a radioactive isotope can be
determined from graphs of number of parent
nuclei versus time and activity level versus time.
• Radioactive isotopes can be used to determine
the age of some materials.
• Carbon-14 has a half-life of 5730 years and is
useful for radioactive dating of material that was
once living.
VOCABULARY
half-life
decay series
CHAPTER
10
Radioactivity and the Atom
• All atoms are made of subatomic particles:
protons, neutrons, and electrons
• Atoms of a single element that differ in mass are called isotopes.
• Isotopes have the same number of protons but vary in the number
of neutrons.
• The isotopes of some elements are radioactive.
• For example uranium-238 and carbon-14.
CHAPTER
10
Radioactivity and the Atom
• Radioactive atoms undergo radioactive decay, which can be written
as nuclear reaction equations.
• There are three basic types of radioactive decay: alpha decay, beta
decay, and gamma decay.
• The rate of decay of a radioactive sample is predictable and is
described by the half-life of the radioactive isotope.
CHAPTER
10
Radioactivity and the Atom
Activity
• Create a mind map with “RADIATION” in the centre.
• Create branches showing all the different types of radiation you can
think of.
• Branch out further describing the uses of these types of radiation in
everyday life (as many as you know).
Uses
Uses
Type
Uses
Type
RADIATION
Uses
• Read 10.1 (pages 275–278) for a better understanding of the different
forms of radiation and their uses.
CHAPTER
10
Radioactivity and the Atom
Key Ideas
• Atoms of a single element that differ in mass are called isotopes.
• The atoms of some elements are radioactive, which means that
they undergo radioactive decay.
• There are three basic types of radioactive decay and these
processes can be written as nuclear reaction equations.
• The rate of decay of a radioactive sample is predictable and is
described by the half-life of the radioactive isotope.