Chapter 25 Nuclear Chemistry
25.1 Nuclear Radiation
Chemistry
Today we are learning to:1. Understand about early discoveries on radioactivity
2. See how an unstable nucleus can release energy
3. Describe 3 types of radiation
Radioactivity
Nuclear Radiation
Born on November 7, 1867, in Warsaw, Poland, Marie
Curie became the first woman to win a Nobel Prize and
the only woman to win the award in two different fields
(physics and chemistry). Curie's efforts, with her
husband, Pierre, led to the discovery of polonium and
radium and, after Pierre's death, the development of Xrays. She died on July 4, 1934.
http://www.biography.com/people/marie-curie9263538
Marie-Curie-Biography
Radioactivity
Nuclear Radiation
In 1896, Antione Becquerel (French) accidentally
showed that uranium salts would fog a
photographic plate.
The Curies demonstrated that the fogging was
caused by rays emitted by the uranium
They called this process radioactivity, and the
rays and particles are called radiation
Radioactivity
Nuclear Radiation
Nuclear reactions differ from chemical reactions in important ways:
i.
In chemical reactions, atoms obtain stable electron configurations by
losing, gaining or sharing electrons.
ii.
In nuclear reactions, the nuclei of unstable isotopes, called radioisotopes,
gain stability by undergoing changes.
The discovery of radioactivity disproves Daltons assumption of indivisible atoms
In radioactive decay unstable radioisotopes are transformed into stable isotopes
releasing large amounts of energy as radiation
Types of Radiation
3 Main types:
i.
Alpha radiation(α – radiation)
ii.
Beta radiation (β – radiation)
iii. Gamma radiation (γ – radiation)
Nuclear Radiation
Nuclear Radiation
Types of Radiation
i.
Alpha radiation(α – radiation)
•
Consists of alpha particles(α – particles)
•
These are high energy helium nuclei which are ejected from a
radioisotope at high velocity (
•
or α)
When an α – particle is emitted:
a)
the atomic number of the nucleus falls by 2
b) the mass number of the nucleus falls by 4
Nuclear Radiation
Types of Radiation
i.
Beta radiation(β– radiation)
•
Consists of beta particles(β – particles)
•
These are high energy electrons which are ejected from a radioisotope
at high velocity (
•
or β)
When a β – particle is emitted:
a) A neutron breaks apart to form a proton and an electron
b) the atomic number of the nucleus increases by 1
c) the mass number of the nucleus stays the same
Types of Radiation
i.
Nuclear Radiation
Gamma radiation(γ – radiation)
•
Consists of very high energy photons (γ – rays)
•
This electromagnetic radiation is often emitted from the nucleus at the
same time as α or β radiation
•
γ – rays:
a) Have zero mass
b) Travel at the speed of light
c) Do not affect atomic number or mass number
Effect of an Electric Field
Nuclear Radiation
Look at the diagram.
1. Write in your notebooks what you can tell about the effect of an
electric field on each type of radiation.
2. Write down what you think may be the reason for the differences in
their deflections
Penetrating Power
Nuclear Radiation
Look at the diagram.
1. Write in your notebooks what you can see about the penetrating
power of each type of radiation.
2. Write down what you think may be the reason for the differences in
penetrating power
25.1
Types of Radiation
Homework questions: Answer Questions 25-32 on page 821 of
your text book for next day (use a periodic table to help identify
products.)
25.1 Section Quiz.
1. Certain elements are radioactive because
their atoms have
a. more neutrons than electrons.
b. an unstable nucleus.
c. a large nucleus.
d. more neutrons than protons.
25.1 Section Quiz.
2. An unstable nucleus releases energy by
a. emitting radiation.
b. thermal vibrations.
c. a chemical reaction.
d. giving off heat.
25.1 Section Quiz.
3. Which property does NOT describe an alpha
particle?
a. 2+ charge
b. a relatively large mass
c. a negative charge
d. low penetrating power
25.1 Section Quiz.
4. When a radioactive nucleus releases a highspeed electron, the process can be described
as
a. oxidation.
b. alpha emission.
c. beta emission.
d. gamma radiation.
2.3 Vocabulary 25.1 Vocabulary
•
•
•
•
•
•
Radioactivity: process where materials give off high energy rays
Radiation: name give to these penetrating rays and particles
Radioisotopes: unstable isotopes that will decay into a different element
Alpha particle: high energy helium nuclei containing 2 protons and 2
neutrons
beta particle: high energy electron emitted from a nucleus
Gamma particle: high energy electromagnetic radiation emitted from a
nucleus
END OF SHOW