Stable And Unstable Atoms - NDE

Skip to main contentAbout NDT and NDECareers in Nondestructive Testing and EvaluationPhysics of Nondestructive EvaluationAtomic Elements

• Basic Structure of Matter
• Atoms and Elements
• Subatomic Particles
• Atom Models
• Stable and Unstable Atoms
• Atomic Number and Mass Numbers
• Elements
• Electrons
• The Valence Shell
• The Free Electron
• Molecules and Compounds
• Chemical Formula
• Isotopes
• Ionization

Electricity

• Things That Work with Electricity
• What is Electricity?
• Electric Charge and Fields
• Electrical Current
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• Direct Current
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• Induction and Inductance
• Self-Inductance and Inductive Reactance
• Mutual Inductance
• Capacitance and Capacitors
• Impedance
• Circuit Diagrams
• Ohm's Law
• Series Circuits
• Parallel Circuits
• Circuits and Phase
• Electromagnetism
• Electrostatic Field
• Electromagnetic Induction
• Creating a Transformer
• Depth of Penetration and Current Density
• Electricity Unit Summary

Magnetism

• Introduction to the Mystery of Magnetism
• Magnetic Behavior
• The Two Ends of a Magnet
• Atoms and Magnetism
• Electron Pairing
• Magnetic Domains
• Ferromagnetic Materials
• Diamagnetic, Paramagnetic, and Ferromagnetic Materials
• Demagnetization
• The Hysteresis Loop
• Permeability
• Magnetic Lines of Force
• Creation of Magnetic Fields
• Magnetic Fields
• Magnetic Field Characteristics
• Electromagnetic Fields
• Electricity and Magnetism
• More on Electricity and Magnetism
• Quantifying Magnetic Properties
• Magnetic Field Produced by a Coil
• Longitudinal Magnetic Fields
• Circular Magnetic Fields: Distribution and Intensity
• Measuring Magnetic Fields
• Magnetization of Ferromagnetic Materials
• Electromagnets
• The Electric Motor and Magnetism

Waves

• Introduction to Waves
• Types of Waves
• Mechanical Wave Characteristics
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• Plane Waves
• Wave Number and Impedance
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• Wave Interaction or Interference
• Refraction and Snell's Law
• Reflection and Transmission Coefficients
• Mode Conversion
• Wavelength and Defect Detection
• Signal-to-Noise Ratio

Sound

• Introduction to Sound
• Sound and Vibration
• Sound Wave Propagation
• Sound Propagation in Elastic Materials
• Modes of Sound Wave Propagation
• The Speed of Sound in Air
• The Speed of Sound in Other Materials
• Temperature and the Speed of Sound
• The Human Ear
• The Components of Sound
• Frequency and Pitch
• The Doppler Effect
• Acoustic Impedance
• Sound Wave Interference
• Refraction of Sound
• Reflection of Sound

X-Ray

• Introduction to X-Rays and Gamma Rays
• Radiographs and Photographs
• The Discovery of Radioactivity
• The Discovery of X-Rays
• The Discovery of Radioactive Elements
• The Curies
• Radioactivity and Radioisotopes
• Radioactive Decay
• Nuclear Reactions
• Radioactive Half-Life
• Radioactive Half-Life (Continued)
• Carbon-14 Dating
• X-Ray Generation
• Nature of Penetrating Radiation
• X-Radiation
• Gamma Radiation
• Activity of Radionuclides
• Isotope Decay Rate
• Ionization
• Newton's Inverse Square Law
• Interaction Between Penetrating Radiation and Matter
• Transmitted Intensity and Linear Attenuation Coefficient
• Half-Value Layer
• Sources of Attenuation
• Compton Scattering
• Geometric Unsharpness
• Filters in Radiography
• Secondary (Scatter) Radiation and Undercut Control
• Radiation Safety

Materials

• Introduction to Structural Materials
• General Material Classifications
• Metals
• Ceramics
• Polymers
• Composites
• Atomic Bonding
• Solid State Structure
• Primary Metallic Crystalline Structures
• Solidification
• Anisotropy and Isotropy
• Crystal Defects
• Elastic/Plastic Deformation
• Fatigue Crack Initiation
• Diffusion
• Property Modification
• Ceramic Structures
• Polymer Structure
• Composite Structures
• Physical and Chemical Properties
• Phase Transformation Temperatures
• Density
• Specific Gravity
• Thermal Conductivity
• Thermal Expansion
• Electrical Conductivity and Resistivity
• Magnetic Permeability
• Corrosion
• Mechanical Properties
• Loading
• Stress and Strain
• Tensile Properties
• Compression, Bearing, and Shear Properties
• Hardness
• Creep and Stress Rupture Properties
• Toughness
• Impact Toughness
• Notch Toughness
• Fracture Toughness
• Fatigue Properties
• S-N Fatigue Properties
• Fatigue Crack Growth Rate Properties

Capillary Action

• Surface Energy
• Specific Gravity
• Viscosity

Nondestructive Evaluation TechniquesNondestructive Evaluation EngineeringGlossaryPhysics of Nondestructive Evaluation > The Atom and Elements > Stable and Unstable Atoms Stable and Unstable Atoms

After reading this section you will be able to do the following:

• Define the terms "strong force" and "binding energy."
• Explain what is meant by a stable atom and and an unstable atom.

Atomic Particle Interaction

There are forces within the atom that account for the behavior of the protons, neutrons, and electrons. Without these forces, an atom could not stay together. Recall that protons have a positive charge, electrons a negative charge, and neutrons are neutral. According to the laws of physics, like charges repel each other and unlike charges attract each other.

Strong Force

A force called the strong force opposes and overcomes the force of repulsion between the protons and holds the nucleus together. The net energy associated with the balance of the strong force and the force of repulsion is called the binding energy. The electrons are kept in orbit around the nucleus because there is an electromagnetic field of attraction between the positive charge of the protons and the negative charge of the electrons.

Atom Stability

In some atoms, the binding energy is great enough to hold the nucleus together. The nucleus of this kind of atom is said to be stable. In some atoms the binding energy is not strong enough to hold the nucleus together, and the nuclei of these atoms are said to be unstable. Unstable atoms are also called radioactive actoms and they will lose neutrons and protons as they attempt to become stable.

Review:

1. The protons stay together in the nucleus because the strong force opposes and overcomes the forces of repulsion from the electromagnetic field.
2. A stable atom is an atom that has enough binding energy to hold the nucleus together permanently.
3. An unstable atom does not have enough binding energy to hold the nucleus together permanently and is called a radioactive atom