Before we dive into the world of electronics, it’s important to step back and ask: what is the true foundation of everything we study in this field?
At the core of every resistor, capacitor, diode, and transistor lies the same fundamental building block — the atom. Whether we talk about current flow, semiconductors, or even the most advanced integrated circuits, all of it begins with the way atoms are structured, how their electrons are arranged, and how these electrons move or interact.
That’s why, before we begin our journey through analog electronics, we first need to understand the atom — its structure, the models that explain it, and the principles that connect atomic behavior to electronic devices. Once this foundation is clear, the rest of electronics becomes much easier to grasp.
So, let’s start at the very beginning — with the atom: the foundation of electronics.
What is an Atom?
An atom is the fundamental building block of all matter. Everything around us — solids, liquids, gases — is made up of atoms. It is the smallest building block of atom that cannot be divided into smaller parts using any chemical means.
Atoms consist of a central nucleus containing positively charged protons and neutral neutrons, surrounded by negatively charged electrons orbiting the nucleus.
History of Atom
The concept of the atom is not new; it dates back more than 2,500 years.
- Greek Philosopher Democritus (460–370 BCE):
He was the first to propose that all matter is made up of tiny, indivisible, and indestructible particles. He called these particles “atomos”, meaning uncuttable or indivisible in Greek. According to him, these atoms moved in a void and combined in different ways to form all matter. - Aristotle’s Opposition:
Another famous philosopher, Aristotle, rejected this theory. He believed matter was continuous and made up of four elements — earth, water, fire, and air. Because Aristotle’s views were more widely accepted, Democritus’ atomic theory was ignored for nearly two millennia. - Resurfacing in the Modern Era:
The idea of atoms re-emerged in the 17th–18th centuries with the development of modern science. - John Dalton (1803): Revived the atomic concept scientifically through his Atomic Theory, which stated that matter is made of indivisible atoms of different types, each element having identical atoms.
- Later, scientists like J.J. Thomson, Rutherford, and Niels Bohr refined the atomic model, discovering subatomic particles (electrons, protons, neutrons) and the nucleus.
👉 The word “atom” thus originated from the Greek word atomos, but its meaning has evolved. What was once thought to be indivisible is now known to have its own internal structure, forming the foundation of modern physics, chemistry, and electronics.
Structure of Atom
Every material we see around us, whether it is a tiny grain of sand, a drop of water, or a large electronic device, is made up of atoms. An atom is extremely small, yet it contains a well-organized internal structure that gives each element its unique properties. At the very center of the atom lies the nucleus, which is a dense and compact region. The nucleus contains two types of particles: protons and neutrons.
Protons carry a positive charge, while neutrons have no charge at all — they are neutral. The number of protons in the nucleus determines the identity of the element. For example, if an atom has one proton, it is hydrogen; if it has six protons, it is carbon; if it has fourteen protons, it is silicon. Neutrons, on the other hand, play the important role of adding stability to the nucleus by balancing the repulsive forces between positively charged protons.
Surrounding this nucleus are very tiny, negatively charged particles called electrons. Electrons do not remain inside the nucleus; instead, they revolve around it in specific paths called orbits or shells. You can imagine the electrons as planets moving around the sun, with the nucleus acting as the sun at the center.
The number and arrangement of these electrons decide how atoms will interact with each other, form bonds, and allow materials to conduct or block electricity. For example, metals like copper have loosely bound outer electrons that move easily, which is why they conduct electricity well. In contrast, insulators like rubber have tightly held electrons that cannot move freely.
Thus, the structure of an atom is a beautiful balance: the nucleus provides mass and stability with protons and neutrons, while the electrons revolving around it determine how the atom behaves in chemical reactions and in electrical conduction. This simple arrangement of particles — protons, neutrons, and electrons — forms the foundation of the entire universe and is the starting point for understanding how electronics truly works.
Curious Questions on Atomic Structure
When we first learn about atoms, many questions naturally come to mind. Let’s try to answer some of the most common ones in simple terms.
Why are protons inside the nucleus and not outside?
Protons carry positive charge, and since like charges repel each other, you might expect them to fly apart. But inside the nucleus, a very strong force called the nuclear force holds the protons together tightly along with neutrons. This force is much stronger than the repulsion between the positive charges, but it only acts over very short distances. That’s why protons stay packed inside the nucleus and do not escape.
Why are electrons outside the nucleus?
Electrons are extremely light compared to protons and neutrons. They are also negatively charged, which means they are attracted to the positively charged nucleus. However, instead of crashing into the nucleus, they keep moving around it in regions called orbits or shells. Their motion is governed by both their energy and the attraction of the nucleus. If electrons were inside the nucleus, the atom would collapse, which nature does not allow.
Why does the strong nuclear force act on protons (and neutrons) but not on electrons? Why can’t electrons be inside the nucleus while protons stay outside?
To understand this, we first need to learn about a concept called quarks.
1. What are quarks?
Quarks are tiny fundamental particles, some of the smallest building blocks of matter.They combine in groups to form protons and neutrons, the particles in the nucleus.Quarks come in different “types” (flavors), but the most common are up and down quarks.
2. How protons and neutrons are made of quarks?
Proton = 2 up quarks + 1 down quark → total charge +1
Neutron = 1 up quark + 2 down quarks → total charge 0
Quarks inside protons and neutrons are held extremely tightly together by the strong nuclear force.
3. Why electrons are different?
Electrons are not made of quarks — they are a completely different type of particle called a lepton.
Because the strong nuclear force only acts on quarks, electrons don’t feel this force at all.
4. Why this determines where particles stay?
Protons and neutrons → feel the strong nuclear force, which holds them together inside the nucleus. Even though protons repel each other electrically, the strong force is much stronger at short distances, so they stay “glued” inside.
Electrons → don’t feel the strong nuclear force, only the electromagnetic attraction from the positively charged nucleus. Quantum mechanics makes them stay in “orbitals” outside the nucleus, rather than crashing in.
✅ Summary in one sentence
Protons and neutrons are made of quarks, so they feel the strong nuclear force and stay inside the nucleus; electrons are not made of quarks, so they don’t feel this force and remain outside, held by electric attraction in allowed energy levels.
Why are neutrons neutral?
Neutrons have no overall charge because they are made of smaller particles (called quarks) whose charges cancel out. Their role is not to attract or repel electrons but to add stability to the nucleus by reducing the repulsion between protons. Without neutrons, most nuclei would be unstable.
Why are protons positively charged and electrons negatively charged?
Protons are made of smaller particles called quarks — specifically, 2 up quarks and 1 down quark. The charges of these quarks add up to give the proton a net positive charge. Electrons, on the other hand, are a different type of fundamental particle called leptons, and they have an intrinsic negative charge. So, protons are positive because of the quarks they contain, and electrons are negative by their very nature. This difference in charge is what allows them to attract each other and form atoms.
We’ll explore charges and quarks in more detail in upcoming blogs.
We’ve now seen that atoms form the very core of all matter and electronics. But what truly gives them their unique behavior is charge — the positive, negative, and neutral nature of subatomic particles. In the next chapter, we’ll dive deeper into these concept of electrons, protons and neutrons, electric charge, the force that governs all of electronics.
