Atomic Models and Structure: From Dalton to Quantum Mechanics
Plum Pudding Model
J.J. Thomson’s identification of negatively charged subatomic particles (electrons) through his study of cathode rays led him to propose a model of the atom. This model, known as the plum pudding model, described electrons as negatively charged “plums” embedded in a “pudding” of positive matter.
Rutherford Model
Based on experiments bombarding thin metal films with alpha particles, Rutherford established the nuclear atomic model. This model describes the atom as consisting of two
Read MoreChemical Equilibrium, Acids, Bases, and Redox Reactions
Chemical Equilibrium
At the beginning of a reversible reaction, the high concentration of reactants results in a fast reaction rate towards product formation. As the reaction progresses and product concentration increases, the reverse reaction rate also increases. Eventually, the forward and reverse reaction rates become equal, establishing a state of chemical equilibrium where the concentrations of reactants and products remain constant.
Equilibrium Constant
The Law of Mass Action states: “In a reversible
Read MoreThermodynamics: Laws, Enthalpy, Entropy, and Gibbs Free Energy
Thermodynamic Processes
A thermodynamic process is the transformation of a system from an initial state of equilibrium to a final state of equilibrium. A system is in equilibrium when it meets the following conditions:
- Chemical Equilibrium: The composition does not change.
- Mechanical Equilibrium: No macroscopically observable movements occur.
- Thermal Equilibrium: The temperature is uniform throughout the system.
These changes can be:
- Reversible: The transformation occurs through a succession of equilibrium
Oxidation and Corrosion: Types, Causes, and Protection Methods
Oxidation and Corrosion
Oxidation
If a substance combines with oxygen, the process is called oxidation, and the resulting combination is called rust.
Examples: film, forge (Fe2O2), carbon dioxide (CO2), aluminum oxide (Al2O3).
Oxidation also releases heat. The more rapid the oxidation, the higher the temperatures reached.
A very rapid oxidation, with a strong development of light and heat, is called combustion.
When oxygen is removed from an oxide, it is called reduction.
Examples: mercury oxide decomposition,
Read MoreMaterials Science: Properties, Degradation, and Shaping Processes
Materials Science
Atomic Structure and Bonding
Atomic Number: Represents the number of protons in an element’s nucleus.
Alloy: A combination of two or more materials, often metals, designed to improve specific characteristics.
Polymer: Materials formed by combining organic molecules into long chains.
Interatomic Spacing: In solids, this refers to the apparent diameter of an atom.
Binding Energy: The energy needed to separate two atoms, reflecting the strength of their bond.
Avogadro’s Number: The number
Read MorePhysical & Chemical Properties of Matter: Atomic Structure Models
Physical Properties of Matter
A physical property is a characteristic that can be observed or measured without changing the substance’s composition. These properties are often revealed during physical processes like changes in state, temperature, or pressure.
Examples include color, hardness, density, boiling point, and melting point.
Physical properties are categorized as:
- Electrical
- Magnetic
- Optical
- Thermal
- Mechanical
Physical properties can be general or specific:
- General properties apply to various substances,