Understanding Electricity: From Atomic Structure to Radioactivity

The Electrical Nature of Matter

Thales of Miletus observed that rubbing amber with a cloth caused both to attract other particles. Benjamin Franklin later suggested that all bodies possess electricity, which can be transferred between them. The three primary methods of electrification are friction, contact, and induction.

The amount of electric charge (Q) is a physical quantity, measured in Coulombs (C). There are two types of electric charge: negative (as found in amber or plastic) and positive (as found in glass). Neutral bodies possess an equal number of positive and negative charges.

Coulomb's Law

Coulomb's Law quantitatively calculates the electric force using the following formula:

F = k * Q1 * Q2 / r²

Where:

• F: Force
• k: Constant of the medium
• Q1 and Q2: Electric charges (in Coulombs)
• r: Distance of separation between charges

Particles of the Atom

The atom is considered indivisible. Its particles include negatively charged electrons and positive protons. A proton's electric charge is approximately 1800 times greater than an electron's. The electron's electric charge is 1.602 × 10^-19 C, and its mass is 9.109 × 10^-31 kg. The proton's electric charge is 1.602 × 10^-19 C, and its mass is 1.673 × 10^-27 kg.

• Cation: An atom that loses one or more electrons and becomes positively charged.
• Anion: An atom that gains one or more electrons and becomes negatively charged.
• Ion: A charged chemical species (i.e., not neutral).

Thomson Atomic Model

This model proposes that the atom is like a continuous sphere of positive charge, with electrons embedded within it due to their much smaller mass compared to protons.

Rutherford Model

The Rutherford model arose from an experiment where Rutherford bombarded a thin sheet of gold with alpha particles (helium nuclei). He observed that most particles passed through the foil undeflected, a few deviated slightly, and very few bounced back. He deduced the following:

• The atom has a central core where most of its mass is concentrated.
• The positive charge of the protons is balanced by the negative electrons revolving around the nucleus.
• Electrons revolve around the nucleus at high speed.

Bohr Model

The Bohr model is based on the following postulates:

• A single electron moves in a circular 'allowed' orbit without emitting energy.
• Electron orbits have specific energy levels, with energy increasing as the orbit moves further from the nucleus.
• When an electron jumps from a higher energy orbit to a lower energy orbit, the excess energy is emitted as radiation, which is observed in spectra.

Electronic Configuration

Electronic configuration describes how electrons are arranged in layers or different energy levels around the nucleus. The maximum number of electrons in each layer is given by the formula 2n², where n is the number of layers.

• 1st layer (K): 2 * 1² = 2 electrons maximum
• 2nd layer (L): 2 * 2² = 8 electrons maximum
• 3rd layer (M): 2 * 3² = 18 electrons maximum
• 4th layer (N): 2 * 4² = 32 electrons maximum

Rules

When the 3rd layer contains 8 electrons, the 4th layer begins to fill, even though the 3rd layer can hold up to 18 electrons. Electrons in the outermost layer are called valence electrons, and the outermost layer is the valence shell.

Atomic Number (Z) and Mass Number (A)

• Z: The number of protons in an atom. All atoms of the same element have the same atomic number. Chemical elements in the periodic table are sorted in increasing order by their atomic numbers.
• A: The number of protons and neutrons in an atom. The mass of electrons is not considered in this calculation.

Isotopes

Isotopes are atoms of an element with the same atomic number but different mass numbers.

Radioactivity

When the number of neutrons in a nucleus is significantly larger than the number of protons, the nucleus becomes unstable and spontaneously emits particles or radiation until it stabilizes. There are three types of radiation:

• Alpha Particles: Helium nuclei with low penetrating power (stopped by a sheet of paper).
• Beta Particles: High-speed electrons with high penetrating power (penetrate aluminum sheets).
• Gamma Radiation: High-energy radiation that propagates at the speed of light, is highly penetrating, and can only be stopped by concrete or lead.