Fundamental Concepts in Physics and Atomic Chemistry

Thermodynamics

Specific Heat

Specific heat is the amount of energy required to raise the temperature of 1 kg of a substance by 1 K.

Latent Heat

Latent heat is the amount of thermal energy transferred to 1 kg of a pure substance to change its state at a constant pressure and temperature.

Heat Engine

Heat engines are devices that transform thermal energy into other forms of energy, such as mechanical work.

Atomic Models

Thomson Atomic Model

Proposed by J.J. Thomson, the discoverer of the electron, this theory describes the atom as a sphere of positive charge containing negatively charged electrons.

Rutherford Model

This model consists of two parts:

• Nucleus: Composed of protons and neutrons, containing nearly all the mass and the total positive electric charge of the atom.
• Electron Cloud: Consisting of electrons orbiting the nucleus.

Bohr Model

1. Electrons move in stable circular orbits at high speeds without radiating energy.
2. Each orbit has a specific energy level; energy increases with distance from the nucleus.
3. When an electron falls from a higher energy level to a lower one, it emits energy.

Atomic Properties

Isotopes

Atoms of the same element that possess a different number of neutrons.

Ions

Atoms that have gained or lost electrons, resulting in a net electric charge.

Mass Number

The sum of the neutrons and protons in the nucleus.

Atomic Number

The total number of protons in an atom.

Chemical Bonding

Covalent Bonds

Occurs between non-metals where electrons are shared rather than transferred. Lewis diagrams are used to represent these atomic bonds.

Ionic Bonds

Occurs between metal and non-metal elements where electrons are donated. Properties:

• Crystalline solids at room temperature.
• High melting and boiling points.
• Hard and brittle.
• Good electrical conductors when fused or dissolved in water.

Metallic Bonds

Occurs between metal atoms, forming a "sea" of negatively charged electrons that attract positive ions. Properties:

• Hard and durable.
• Good conductors of electricity and heat.
• Possess a metallic luster.