Chapter 25 Nuclear Chemistry

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16 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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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 X
-
rays. She died on July 4, 1934.

http://www.biography.com/people/marie
-
curie
-
9263538

Marie
-
Curie
-
Biography



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

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

Nuclear Radiation

3 Main types:

i.
Alpha radiation(
α



radiation)


ii.
Beta radiation (
β



radiation
)

iii.
Gamma radiation (
γ



radiation)



Types of Radiation

Nuclear 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



Types of Radiation

Nuclear 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

Nuclear Radiation

i.
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

Types of Radiation


25.1

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 high
-
speed 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