Basic Electricity and Atomic Theory

Foundations of Energy and Electric Charge

Energy is multifaceted and can be defined in various ways depending on its application and context. It is fundamentally described as the ability to perform work, but it also comprises all matter in the universe. Beyond these definitions, the presence of energy is so significant that it affects the fundamental structure of space, influencing both gravity and the progression of time. Electricity is a specific and essential manifestation of energy that powers the modern world. It is the primary force responsible for all chemical reactions occurring in nature. Electricity can be observed traveling through the atmosphere in the form of lightning or passing through matter as radio waves and other electromagnetic frequencies. Furthermore, electricity surrounds the planet with a protective shell of magnetism and is harnessed by humanity to power the majority of modern technological devices.

The history of electricity traces back to ancient Greece, where writers first described its phenomena. The Greeks discovered that when amber, which is fossilized tree resin or sap, was rubbed against fur, it acquired the ability to attract light objects such as feathers or straw. It is from the Greek word for amber, "Electron," that the modern term electricity is derived. Historically, experiments involving the rubbing of various materials together revealed that charged objects could interact across space without physical contact. These interactions led to the discovery of the Law of Charges, which states that "Like" charges repel each other, while "Opposite" charges attract each other. In early experimentation, substances were categorized into groups (referred to as List A and List B); items within the same list would repel each other, while an item from List A would be attracted to an item from List B.

Evolution of the Atomic Model

The conceptualization of the atom has evolved significantly over the centuries. The term "Atom" originates from the Greek word for "indivisible." In $1808$ , John Dalton proposed that all matter was composed of these discrete, indivisible units. However, this view was challenged in $1897$ when J.J. Thompson discovered the electron. This particle had a mass less than $1/1000th$ the mass of a hydrogen atom, proving that the atom was not indivisible but rather consisted of separate constituent parts. In $1900$ , Max Planck introduced the concept of the "quantum," which Albert Einstein later used in his theories regarding quantum light. In $1913$ , Neils Bohr applied these quantum theories to modify the Rutherford model of the atom, creating the Bohr model commonly taught today. This model describes a negatively charged electron circling a positively charged proton, as seen in the hydrogen atom.

Quantum effects identified by Planck and Einstein dictate that electrons cannot exist in arbitrary locations around the nucleus; they can only occupy specific orbits known as "Orbital Shells." There are no spaces for electrons between these shells. The physical forces within these structures are immense. As noted by Richard Feynman, the electric force is so powerful that if two people standing beside each other had a mere $1$ % imbalance in their number of electrons, the resulting force would be sufficient to lift the entire planet Earth. On a microscopic scale, two protons located in the nucleus of an atom repel one another with a force of approximately $23.5\,kg$ .

Atomic Composition and the Periodic Table

Every element is defined by the specific type of atom that comprises it. The identity and atomic number of an element are determined solely by the number of protons located in the nucleus. In a stable atom, the number of protons is always equal to the number of electrons. For instance, Hydrogen has an atomic number of $1$ because it contains one proton. While protons and neutrons reside in the nucleus and provide the vast majority of the atom's atomic weight, the electron is much less massive. A proton weighs $1840$ times as much as an electron, yet an electron is physically $3$ times as large as a proton. Neutrons, which were not discovered until $1932$ , have no electrical charge but possess a mass slightly greater than that of a proton.

The periodic table organizes elements based on their atomic number and valence electrons. Examples include Hydrogen ( $H$ , atomic number $1$ , valence electron $1$ ), Helium ( $He$ , atomic number $2$ , valence electrons $2$ ), Lithium ( $Li$ , atomic number $3$ , valence electron $1$ ), and Copper ( $Cu$ , atomic number $29$ , valence electron $1$ ). Larger atoms require more protons, neutrons, and electrons. For comparisons of scale, the nucleus of a Helium atom contains $2$ protons and $2$ neutrons, whereas the nucleus of a copper atom contains $29$ protons and $35$ neutrons. Molecules are created when a collection of atoms is electrically bound together. A molecule consisting of only one type of atom is a molecule of an element (such as $O_2$ gas, Gold, Iron, Coal, Oil, Diamond, Graphite, or Graphene). If a molecule contains different types of atoms, it is a compound, such as Carbon Dioxide ( $CO_2$ ), Water ( $H_2O$ ), Salt ( $NaCl$ ), or Sucrose ( $C_{12}H_{22}O_{11}$ ).

The Four Fundamental Forces of Nature

Modern physics identifies four fundamental forces that govern the universe and hold the atom together despite the intense repulsion between protons. These are the Strong Nuclear force, the Weak Nuclear force, Electromagnetism, and Gravity. The Strong Nuclear force is the most powerful; it is $137$ times stronger than electromagnetism, $100,000$ times more powerful than the weak force, and approximately $6 \times 10^{39}$ times more powerful than gravity. However, it only operates across extremely short distances, approximately $10 \times 10^{-15}$ meters or $0.0000000000000001\,m$ . If protons are separated by more than this distance, the electromagnetic force takes over and pushes them apart. The Weak Nuclear force is responsible for atomic decay. At extremely high energy levels, the Weak Nuclear force and Electromagnetism are believed to unify into a single force, and it is theorized that at even higher energies, the Strong Nuclear force also joins this unification. These forces operate through the exchange of subatomic particles: Photons carry electromagnetism, W and Z Bosons carry the weak force, and Gluons carry the strong force. Gravity remains poorly understood, though scientists hypothesize the existence of a particle called the "Graviton."

Orbital Shell Mechanics and Valence Electrons

Electrons within an atom are subject to two primary forces: they are attracted to the protons in the nucleus by electromagnetic attraction and repelled by other electrons. This repulsion limits how close they can get to one another. In a hydrogen atom, electrons can reach speeds of approximately $1/137th$ the speed of light, which equates to $2,189.78\,km/sec$ , though they can approach the full speed of light under certain conditions. Each orbital shell has a strict limit on the number of electrons it can contain. This limit is determined by the formula $2 \times N^2$ , where $N$ is the number of the orbit. In the first shell ( $N=1$ ), there can be up to $2 \times (1)^2 = 2$ electrons. The second shell ( $N=2$ ) can hold up to $2 \times (2)^2 = 8$ electrons. The third shell ( $N=3$ ) can hold up to $2 \times (3)^2 = 18$ electrons, and the fourth shell ( $N=4$ ) can hold up to $2 \times (4)^2 = 32$ electrons. Currently, $32$ is the maximum number of electrons observed in any single shell.

The electrons in the outermost orbit are known as Valence Electrons, and they are responsible for the chemical properties of the atom. If an atom loses a valence electron, it becomes a positively charged ion. If it gains an electron from its environment, it becomes a negatively charged ion. These charged atoms are generally more chemically reactive. Material properties are determined by these valence electrons. Conductors typically have $1$ , $2$ , or $3$ valence electrons. For example, Copper ( $2, 8, 18, 1$ ) is a conductor because its single lone valence electron is easily displaced by an incoming electron. Insulators typically have $5$ , $6$ , or $7$ valence electrons; in these materials, the energy of an incoming electron is dissipated among the existing valence electrons, making it difficult to dislodge them. Neon is a prime example of an insulator; it has a full valence shell, making it inert and resistant to chemical reactions. Semiconductors possess exactly $4$ valence electrons and are used in the creation of electronic components by being mixed with other substances.

Electromotive Force (EMF) and Its Sources

Electromotive Force, commonly abbreviated as EMF, refers to the movement of electrons through a conductor, which we recognize as electricity. Electrons are the smallest stable particles with a non-zero charge and a low mass that serve to bind matter together. There are six recognized methods for generating EMF:

Magnetism: Moving a magnetic field past a conductor pushes the electrons within that conductor. This principle is utilized in voice coils for speakers, where magnets and signals interact to move air and create sound waves.
Chemical Action: This is the method used in batteries. A Zinc-Copper Voltaic cell, for instance, uses a zinc electrode in zinc sulfate solution (the anode), a copper electrode in copper sulfate solution (the cathode), and a salt bridge to produce electricity for devices like light bulbs.
Pressure: Creating a physical bend in certain crystals generates electricity. This phenomenon is known as piezoelectricity. Conversely, applying a voltage to these same crystals will cause them to bend.
Heat: Electricity can be produced by heating the junction between two dissimilar metals. A device called a thermocouple uses this principle to measure temperature via electrical output. Large arrays of thermocouples, powered by heat from radioactive isotopes, provide electricity for spacecraft traveling into deep space, such as the Voyager, Galileo, and Cassini probes.
Friction: Rubbing materials together, such as the ancient Greek example of amber and fur, generates electrical charge.
Light: Light consists of photons, which are virtually massless force-carrying particles belonging to the Lepton family. When photons impact certain metals, their dual wave-particle nature causes electrons to flow. Additionally, when metal is heated significantly, it emits photons.