Fundamentals of Atomic Structure and Material Properties

Atomic Structure of Matter

Atomic structure of matter refers to how substances can take crystal conformation in industrial processes and treatment.

Elementary Particles

These particles make up the atom (electron, proton, positron). The main characteristics of an atom are its mass and electric charge.

The Atom

An atom is considered to consist of a nucleus, where protons and neutrons stand. The nucleus holds the mass and positive charge of the atom. When an atom is not excited, it is electrically neutral, meaning the number of electrons equals the number of protons. In the nucleus are positively charged protons and neutral neutrons.

Peripheral Electrons

Peripheral electrons within atoms determine their physical and chemical properties. The energy level of an electron is determined by the distance of its orbit from the nucleus. When electrons undergo a transformation, their energy changes, e.g., by absorbing energy to move from an inner to an outer orbit. Example: When a body is heated, it expands as electrons move from inner to outer orbits; they move from outer to inner orbits when cooling.

Metals

Metals are elements with a tendency to yield electrons; they are good conductors of heat and electricity. E.g., metallic sodium.

Non-metals

Non-metals are elements that tend to capture electrons; they are poor conductors of electricity.

Types of Chemical Bonds

Ionic Bond

Formed between ions of different charges.

Covalent Bond

Formed when non-metal elements chemically bind. There is no complete transfer of electrons, but a mutual penetration of the outermost electron orbits, forming a common electron cloud.

Metallic Bond

Metals have the following characteristics:

• Metallic luster after polishing
• The color is typically gray, white, or yellow.
• Are good conductors of heat and electricity.
• Crystal structure is polyhedral.
• Crystals can deform without breaking.

A metallic bond is a mixture of ionic and covalent characteristics. Free electrons move through the atoms, forming a common electron cloud. The brightness of a metal is due to this electron cloud.

Crystalline State

When the transition from liquid to solid occurs abruptly under certain pressures and temperatures, crystals appear. Atoms are grouped, forming polyhedra known as crystal lattices.

Types of Crystalline Substances

Ionic Crystals

They are hard and brittle with high melting points.

Covalent Crystals

They are hard, brittle, poorly deformable, and poor conductors of electricity.

Metallic Crystals

They can be soft and easily deformed (ductile), lustrous, and good conductors of heat and electricity.