CHEM 1E CHAPTER 3

Definition: Engineering materials refer to materials used in constructing man-made structures.
Primary Function: These materials must withstand applied loads without breaking or excessive deflection.

The ideal material serves the desired purpose at minimal cost by considering:
1. Availability of the materials
2. Suitability for working conditions
3. Cost of materials

Definition: An atom is the smallest unit of matter retaining the chemical properties of an element.
Combination: Atoms combine to form molecules, which interact to make solids, gases, or liquids.

Composition of Atoms: Consist of three basic particles:
- Protons: Positively charged
- Neutrons: Neutrally charged
- Electrons: Negatively charged.
Nucleus: Contains protons and neutrons, while electrons reside in shells around the nucleus.

Atomic Number (Z): Number of protons in an atom.
Mass Number (A): Sum of protons and neutrons.
- Formulas:
  - Number of Protons = Atomic Number
  - Mass Number = Protons + Neutrons

A neutral atom has equal numbers of protons and electrons, leading to a total electric charge of zero.
When electrons are gained or lost, atoms become ions, acquiring a positive or negative charge.

Displays atomic numbers, symbol representation, and elemental classifications, such as metals, nonmetals, and metalloids.

Definition: Used to describe electron distribution in atoms.
Types of quantum numbers:
1. Principal Quantum Number (n): Indicates the electron shell level based on distance from the nucleus.
2. Angular Quantum Number (l): Defines the shape of the orbital.
3. Magnetic Quantum Number (m): Specifies the orientation of an orbital.

Determines the most probable distance of an electron from the nucleus, with larger n indicating farther electrons and larger atomic sizes.

Determines atomic orbital shapes and ranges from 0 to n-1, with each value representing a different subshell (e.g., s, p, d).

Specifies the orientation within a subshell, with the number of orbitals in a subshell given by:
- Number of orbitals = 2l + 1

Describes how electrons are distributed across various orbitals, following the Aufbau Principle, Pauli Exclusion Principle, and Hund’s Rule.
Aufbau Principle: Electrons fill the lowest energy orbitals first.
Pauli Exclusion Principle: No two electrons can have the same set of four quantum numbers.
Hund's Rule: Each orbital in a subshell receives one electron before pairing begins.

Definition: Formation of compounds by joining atoms through chemical bonds, which involve electron sharing or transfer.

Occur when electrons are transferred from one atom to another, forming charged ions that attract each other.

Involves sharing a pair of valence electrons between atoms that leads to stable molecules.

Involve the attraction between delocalized electrons and positive metal ions, contributing to materials' structural presence and unique properties.

Metals: Strongest materials, often utilized in various applications.
- Ferrous Metals: Contain iron (e.g., ferrous alloys, carbon steels).
- Non-Ferrous Metals: Lighter, corrosion-resistant materials (e.g., aluminum, copper).
Composites: Fabricated from two or more constituent materials, offering unique properties.
Polymers: Includes plastics and elastomers.
Ceramics: Durable and heat-resistant materials, often brittle but useful for specific applications.

Understanding the chemistry of engineering materials helps engineers select appropriate materials for various applications, serving as a foundation for structural integrity and functionality.