NUCLEAR CHANGE
Nuclear Change
Nuclear change:
Definition: when an unstable nucleus
spontaneously changes to form a more stable
nucleus
Involves the release of particles, electromagnetic
waves or both
This process is called:
RADIOACTIVITY!
Nuclear Change
Types of radiation:
1.Beta particle (β particle) – charged electron
emitted during a certain type of radio active decay,
known as beta decay
2.Beta Decay stabilizes nuclei by converting
neutrons to protons
n
p + e-
Important
Point!
In Beta decay, a neutron emits a
high-energy electron (a beta
particle) and changes into a
proton!
Nuclear Change
If an element adds a proton to its nucleus
by Beta decay, then we must have……
Nuclear Change
Formula for beta decay:
1 n
1 p +
0
+1
0 e
-1
For example, carbon-14 can beta decay to
Nitrogen 14
14 C
14 N + 0 e
6
7
-1
Nuclear Change
Result of Beta Decay:
1. Neutron turns into a proton forming a new element
2. Atomic number increases by 1
3. Mass number stays the same
4. Electron (beta particle) is emitted
http://library.thinkquest.org/3471/radiation_types_body.html
Nuclear Change
Alpha Decay
 Stabilization of nuclei by losing alpha
particles
Alpha particle: helium nucleus
 2 protons and 2 neutrons
From: http://library.thinkquest.org/3471/radiation_types_body.html
Nuclear Change
Why does alpha decay happen?
If a nucleus contains too many protons, then
excessive repulsion of like charges occurs
In an attempt to stabilize the nucleus, an alpha
particle is emitted
The nucleus splits in two pieces:
One piece: alpha particle
Second piece: a nucleus reduced by two protons and
two neutrons
Nuclear Change
Result of Alpha Decay:
1. Atomic numbers decreases by 2 – new element is formed
2. The mass number has decreased by 4 amu
3. Alpha particle goes zooming away from the original nucleus
Nuclear Change
Gamma Rays – Electron Capture
Produced when a proton “captures” an
electron from the orbital nearest the nucleus
and changes into a neutron
Decreases the atomic number by one
This process causes an “excited nucleus”
A gamma ray is emitted by the nucleus to
become more stable
Nuclear Change
Electron is absorbed by the nucleus
Gamma Ray
Proton turns into
a neutron
Result:
1. Atomic number decreases by one to form a new element
2. Mass number stays the same
2. Gamma ray is released
From: http://library.thinkquest.org/3471/radiation_types_body.html
Nuclear Change
Gamma Rays – Positron Emission
Positron – antiparticle of the electron!
The opposite of an electron
Proton emits a positron and becomes a
neutron
The positron seldom makes it out of the atom
because it collides with an electron ,
ANNIHILATION OF MATTER OCCURS
All the mass of the two particles are
converted into gamma rays
Nuclear Change
Proton gives off a
Positron and becomes
a neutron
Results of positron emission:
1. Proton becomes a neutron
2. Atomic number changes
3. Element changes
4. Mass number stays the same
5. Positron emitted, but annihilated by an electron
6. Gamma rays given off
Positron is
usually
annihilated
by an
electron
Nuclear Change
Nuclear Equations MUST BE BALANCED!
Due to the Laws of Conservation of
Mass and Energy!
1. Mass numbers must be the same on both
sides
2. Total atomic numbers must be the same on
both sides (nuclear charges must balance)
3. If atomic number changes, the identity of
the element must change