1. NUCLEAR CHANGE

2. RADIOACTIVITY! 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!

3. Nuclear Change
Types of radiation:
Beta particle (β particle) – charged electron emitted during a certain type of radio active decay, known as beta decay
Beta Decay stabilizes nuclei by converting neutrons to protons
In Beta decay, a neutron emits a high-energy electron (a beta particle) and changes into a proton!
n p + e-
Important
Point!

4. Nuclear Change
If an element adds a proton to its nucleus by Beta decay, then we must have……

5. Nuclear Change Formula for beta decay: 10n 1+1 p + 0-1e
For example, carbon-14 can beta decay to Nitrogen 14
146C N + 0-1e

6. 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

7. Nuclear Change Alpha Decay
Stabilization of nuclei by losing alpha particles
Alpha particle: helium nucleus
2 protons and 2 neutrons
From:

8. 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

9. 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

10. 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

11. 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:

12. 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

13. Nuclear Change Proton gives off a Positron and becomes a neutron
Positron is
usually
annihilated
by an electron
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

14. Nuclear Change Nuclear Equations MUST BE BALANCED!
Due to the Laws of Conservation of Mass and Energy!
Mass numbers must be the same on both sides
Total atomic numbers must be the same on both sides (nuclear charges must balance)
If atomic number changes, the identity of the element must change