Atomic Theory and Chemical Bonding: Exploring Subatomic Particles
Atomic Theory and Chemical Bonding
Early Atomic Experiments
In the late 19th and early 20th centuries, experiments involving electrical discharges through low-pressure gases and particle bombardment of radioactive gases and thin metal sheets revealed the divisibility of atoms and the existence of subatomic particles.
Key Discoveries:
- 1897: J.J. Thomson discovered the electron.
- 1911: Ernest Rutherford identified the atomic nucleus.
- 1932: James Chadwick discovered the neutron.
Atomic Models
Thomson’s Model:
Read MoreDalton’s Atomic Theory and the Structure of the Atom
Dalton’s Atomic Theory and Molecules
Dalton
Dalton’s theory aimed to explain the experimental laws of matter and served as a precursor to modern chemistry. He built upon the theories of Democritus and revived the concept of atoms.
Atom: The smallest part of a chemical element that retains the properties of that element.
Dalton’s Atomic Theory
- Matter is made of tiny, indivisible particles called atoms.
- Atoms of the same element are identical and have the same shape, size, and mass.
- Atoms of different elements
Materials and Their Applications: A Comprehensive Guide
Materials and Their Applications
1. Introduction to Materials
Materials are substances that make up everything around us. Each material possesses unique physical, chemical, and mechanical properties that determine its suitability for specific purposes. Key mechanical properties include hardness, toughness, weakness, elasticity, malleability, and plasticity.
Desirable material characteristics:
- Suitability for intended use
- Easy recyclability with minimal energy consumption and pollution
- Minimal waste generation
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