Colloids: Properties, Types, and Applications in Industry
Colloids: Systems with Dispersed Particles (1-100 nm)
Colloids represent an intermediate state between solutions and suspensions. They consist of a dispersed phase (like micelles) within a dispersant medium. Key characteristics include particle size, coating type, interface properties, settling behavior, and separation methods.
Comparison of Dispersions
- Solutions (<1 nm): Homogeneous, no settling, not separable by filtration.
- Colloids (1-100 nm): Heterogeneous, high surface area, no settling, not
Evolution of Atomic Models: From Dalton to Quantum Mechanics
Dalton’s Atomic Model
In 1808, Dalton formulated his atomic theory, which broke with traditional ideas (Democritus, Leucippus). It introduces the concept of the discontinuity of matter, being the first scientific theory to consider that matter is divided into atoms. The basic postulates of this theory are:
- Matter is divided into particles called atoms, which are indivisible and unchangeable.
- Atoms are very small particles and cannot be seen with the naked eye.
- All atoms of the same element are equal
Chemical Bonding: Ionic, Covalent, and Metallic Properties
Ionic Bonds
An ionic bond unites ions with opposite charges through electrostatic attraction. Lattice energy, released during ionic bond formation from gaseous ions, determines the bond’s stability. Higher lattice energy indicates stronger attraction and a more stable ionic network.
Properties of Ionic Compounds
- Solids at room temperature, forming crystal lattices.
- High melting and boiling points due to strong electrostatic forces.
- Hard and brittle due to low compressibility.
- Soluble in polar solvents
Chemical Bonding & Periodic Table Essentials
Molecular Union & Crystal Structure
Molecular union of atoms results in discrete groups. Network crystals have millions of atoms ordered regularly. Chemical linkage is the force of attraction holding atoms in a molecule or crystal, known as chemical bonds.
Octet Rule
Atoms of different chemical elements tend to unite to achieve stability by having eight electrons in their last layer, called the octet.
Ions
Cation: Metallic element losing electrons, positively charged.
Anion: Non-metallic element gaining
Nuclear Reactors and Radioactivity Essentials
Nuclear Reactor Basics
A nuclear reactor is an installation where nuclear reactions occur. Key components include:
- Fuel Rods: Mixed uranium-containing aluminum, allowing fluid circulation.
- Reactor Core: Contains fuel rods, typically cooled with H2O.
- Control Rods: System to start or stop nuclear fission chain reactions.
- Moderator: Ensures continuity in the chain reaction by managing neutron speeds.
- Refrigerant: Removes fission heat by plunging into the nucleus.
- Shield: Biological shield preventing radiation
Evolution of Atomic Models: From Democritus to Quantum Mechanics
First Atomic Models
Democritus (450 BC)
Proposed the idea of atoms as indivisible particles.
Dalton Atomic Model
Introduced atomic-molecular theory:
- Matter consists of indivisible atoms.
- Atoms of the same element have identical mass and properties.
- Compounds form from combinations of different elements.
- Mass is conserved in chemical reactions.
- Law of multiple proportions.
Lavoisier: Law of Conservation of Mass
Proust: Law of Definite Proportions
Atomic Model – Thomson
Discovered electrons through cathode ray
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