Fundamentals of Atomic Structure and Nuclear Energy

Electric Nature of Matter

Matter undergoes electric phenomena. It can be uncharged (neutral), positively charged, or negatively charged.

• Like charges repel, and opposite charges attract.
• A body is neutral when it has an equal number of positive and negative charges.
• A positively charged body has more positive charges than negative charges.
• A negatively charged body has more negative charges than positive charges.

Electric charge in various media, and the forces exerted between charges, are described by Coulomb's Law.

Coulomb's Law

The force (F) between two point charges (Q₁ and Q₂) is directly proportional to the product of the charges and inversely proportional to the square of the distance (D) between them.

F = k * (Q₁ * Q₂) / D²

Where:

• Q: Electric Charge (Coulombs)
• k: Coulomb's Constant (approximately 9 x 10⁹ N·m²/C²)
• F: Force (Newtons)
• D: Distance (meters)

Key principles of Coulomb's Law:

• The greater the magnitude of the charges (Q), the greater the force (F).
• The greater the distance (D) between the charges, the smaller the force (F).
• Attraction occurs between opposite charges (e.g., positive and negative).
• Repulsion occurs between like charges (e.g., positive and positive, or negative and negative).

Subatomic Particles

• Proton: Positively charged (+1e), located in the nucleus, has significant mass.
• Neutron: No charge (neutral), located in the nucleus, has significant mass (approximately equal to a proton).
• Electron: Negatively charged (-1e), orbits the nucleus, has negligible mass compared to protons and neutrons.

Atomic Models

Thomson Model (Plum Pudding Model)

Proposed that an atom is a sphere of uniformly distributed positive charge (the 'pudding') with negatively charged electrons ('plums') embedded within it. The total positive charge equals the total negative charge, making the atom neutral.

Rutherford Model (Planetary Model)

Based on his gold foil experiment, Rutherford concluded that:

• Matter is practically empty space.
• There is a very small, dense region at the center where most of the atom's mass is concentrated, called the atomic nucleus.
• The positive charge is concentrated in this small nucleus.
• Electrons orbit the nucleus in a 'cortex' or electron cloud.

Bohr Model

• Electrons orbit the nucleus in specific, stable orbits (energy levels) without emitting energy.
• Electrons in orbits farther from the nucleus have higher energy.
• When an electron moves from one orbit to another, it must gain or lose a specific, quantized amount of energy.

Atomic Structure and Properties

Atomic Number, Mass Number, and Isotopes

• Atomic Number (Z): The number of protons in an atom. It uniquely defines an element.
• Mass Number (A): The total number of protons and neutrons in an atom's nucleus.
• Isotopes: Atoms of the same element (same atomic number Z) but with different numbers of neutrons (and thus different mass numbers A).

Electron Distribution in Shells

Electrons are distributed in shells (energy levels) around the nucleus, each with a maximum capacity:

• Shell 1: Up to 2 electrons
• Shell 2: Up to 8 electrons
• Shell 3: Up to 18 electrons
• Shell 4: Up to 32 electrons

Ions

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

• Cation: A positively charged ion formed when an atom loses electrons (number of protons > number of electrons).
• Anion: A negatively charged ion formed when an atom gains electrons (number of protons < number of electrons).

Atomic Mass

The average mass of an atom of an element, calculated by taking the weighted average of the masses of all its naturally occurring isotopes, relative to Carbon-12 (¹²C).

Radioactivity

The spontaneous process by which unstable atomic nuclei emit radiation to become more stable.

Types of Radiation

• Alpha (α) Particles: Heavy, positively charged particles (helium nuclei, ⁴He). They are slow and have low penetrating power.
• Beta (β) Particles: Light, negatively charged particles (high-energy electrons). They are fast and have higher penetrating power than alpha particles.
• Gamma (γ) Rays: High-energy electromagnetic radiation (photons) with no charge or mass. They travel at the speed of light and have very high penetrating power.

Nuclear Energy Production

Nuclear Fission

The process of splitting a heavy, unstable atomic nucleus into two or more smaller, more stable nuclei, accompanied by the release of a large amount of energy. Energy is obtained from the conversion of a small amount of mass into energy (E=mc²).

Nuclear Fusion

The process of combining two light atomic nuclei to form a heavier, more stable nucleus, releasing a tremendous amount of energy. This is the energy source of stars.