Transcript Nuclear Chemistry

Nuclear Chemistry
Chapter 25
What do you think of when you
hear Nuclear Chemistry?

Henri Becquerel (1852-1908)
◦ Originally thought sunlight caused uranium to
radiate
◦ Discovered the spontaneous radiation while waiting
for a sunny day to test his theory

Marie Curie (1867-1934) and her husband
Pierre Curie (1859-1906)
◦ Worked w/ Becquerel
◦ Eventually showed that the rays were from uranium
atoms
◦ Came up with the term “radioactivity” to describe

Radiation – penetrating rays and particles
emitted by a radioactive source.
History
An unstable nucleus releases energy by
emitting radiation during the process of
radioactive decay.
 What is an unstable nucleus?

◦ Stability depends of the neutron to proton
ratio.
◦ Atoms with low atomic numbers (1-20) have a
1:1 ratio.
◦ Above 20, stable nuclei have a 1.5:1 ratio.
◦ Alpha Decay - Alpha Decay, Alpha Particles,
Radioactivity - PhET
Radiation

Alpha Radiation- when a helium nuclei has
been emitted from a radioactive source.
Types of Radiation

Beta Radiation – An electron resulting
from the breaking apart of a neutron in an
atom.
Types of Radiation
Gamma Radiation – a high-energy photon
emitted by a radioisotope.
(electromagnetic radiation)
 Extremely Dangerous!

Types of Radiation

ALPHA
◦ Positive matter
◦ Exactly like a Helium
nucleus

BETA
◦ Negative matter
◦ Exactly like an
electron

GAMMA
◦ High energy wave
◦ NOT matter so no
charge
Summary of Radiation

neutron to proton ratio determines the
type of decay

Four Types of Decay
 Beta Decay
 Electron Capture
 Positron Emission
 Alpha Decay
Types of Decay
Too Many Neutrons!
 Beta Decay – neutron turned into a proton
and electron

1
0
1
n
1
H +
0
-1
e
Example:
14
6
14
C
Beta Decay
7
0
N
+
-1
e
Too few neutrons!
 Electron Capture – convert proton to
neutron; an e- is captured.

Example:
37
18
Ar
+
0
-1
e
Electron Capture
37
17
Cl
Positron – particle with the mass of an
electron but a positive charge
 A proton changes to a neutron.

Example:
8
5
B
8
4
Be
+
Positron Emission
0
+1
e
Too many neutrons and too many
protons!
 Most common in atoms with an atomic
number greater than 83.
 Alpha Emission – release of an alpha
particle.

Example:
226
88
Ra
Alpha Decay
222
86
Rn +
4
2
He
The blue ones have at least one stable isotope. Others do not!
http://catalog.flatworldknowledge.com

Half-life: is the time required for one half
of the nuclei of a radio isotope sample to
decay to stable products.
Half-Life