Atomic Models: Thomson, Rutherford, and Bohr’s Contributions
Atomic Models: Thomson, Rutherford, and Bohr
JJ Thomson proposed the first model of the atom: electrons are like plums embedded in a positive charge ‘pudding’. The positive charge of the ‘pudding’ exactly compensated for the negativity of the electrons, making the atom electrically neutral.
Rutherford: When alpha particles are fired at a thin gold foil, some are deflected. This indicates that there is a zone (nucleus) where the positive charge is concentrated, and a mass greater than or comparable
Read MoreChemical Reactions: Alcohols, Aldehydes, Ketones, Esters, and Acids
Alcohols: Substitution, Combustion, and Elimination Reactions
Substitution reaction: CH3CH2OH + HCl → CH3CH2Cl + H2O
Combustion reaction: Produces CO2 + H2O
Obtaining Alcohols:
- Hydrolysis of alkyl halides.
- Hydration of alkenes catalyzed by acids.
Elimination reactions (Dehydration):
- Elimination of H2O from alcohols.
- Reaction with strong dehydrating agents yields alkenes.
- Removal of water from two alcohol molecules forms an ether. This depends on the temperature and the alcohol ratio.
Examples:
- CH3CH2OH →
Atmospheric Pressure, Gas Laws, States of Matter, and Elements
Item 3: Atmospheric Pressure and Gas Laws
Atmospheric Pressure: The pressure exerted by the atmosphere due to its weight on the surface of bodies in contact with it.
Boyle’s Law: At a constant temperature, the volume occupied by a given mass of a gas is inversely proportional to the pressure. This can be expressed as: P1 x V1 = P2 x V2.
Gay-Lussac’s First Law: If the gas pressure remains constant, the volume of a fixed mass of gas is directly proportional to the absolute temperature. The increase
Read MoreUnderstanding Electrostatics: Principles, Models, and Applications
Electrostatics: An Introduction
Electrostatics is the study of electric charges at rest. This field explores the phenomena associated with stationary electric charges and their interactions.
Early Discoveries
The history of electrostatics dates back to ancient times:
- Thales of Miletus: Observed that rubbing amber with cat fur attracted feathers.
- William Gilbert: Manufactured the versorium, a device to detect electric charge.
- Charles du Fay: Noted that rubbing glass with silk electrified objects, leading
Understanding Chemical Bonds: Covalent, Ionic, and Metallic
Covalent bonds: A covalent bond is formed when two atoms share electron pairs, allowing the atoms to achieve an external configuration that satisfies the “Octet Rule”: 8 (eight) or 2 (two) electrons.
Types of Covalent Bonds
Covalent bond – common: A shared electron pair is formed by one electron from each of the atoms involved. This bond can occur between two similar atoms, resulting in a nonpolar covalent bond, or between different atoms, resulting in a polar covalent bond.
- Nonpolar Covalent Bond:
Energy, Thermodynamics, and Thermochemistry Concepts
Energy, Thermodynamics, and Thermochemistry
Energy: The ability of a body or system to produce work or heat transfer. Energy is neither created nor destroyed, only transformed.
Chemical Energy: The energy due to associations between atoms, ions, and molecules that make up each substance. It accumulates in the chemical bonds and joints caused by intermolecular forces.
Work: A mechanism of energy transfer between bodies based on the use of force.
Heat: Thermal energy is transferred naturally or spontaneously
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