Lesson Fundamentals and Ohm’s Law · Atom and materials
Atomic structure
Every wire, breaker, and motor starts with matter. The atom has three principal parts: proton (+), electron (−), and neutron (no charge). The nucleus is positive; electrons orbit outside. Current is electron movement — but first you need the map of the atom.
What we are trying to understand
Before Ohm, cables, and breakers, this lesson answers: what is matter made of that can conduct?
You will handle:
- The three principal parts of an atom and their charges.
- Atomic number (element identity).
- The Bohr model idea (shells / orbits).
- Why this matters to the electrician (electrons can move).
The three principal parts
| Particle | Charge | Location | Field note |
|---|---|---|---|
| Proton | Positive (+) | Nucleus | Defines the element |
| Neutron | None (0) | Nucleus | Adds mass; no net charge |
| Electron | Negative (−) | Orbits / shells outside nucleus | Moves → current |
Protons and neutrons are vastly more massive than electrons (on the order of ~1836 times). The electron is tiny, but it is the star of electric current.
Hydrogen and helium: the simplest examples
- Hydrogen: 1 proton + 1 electron (simplest atom; teaching model often shows no neutron).
- Helium: 2 protons + 2 neutrons + 2 electrons (smallest common example that includes neutrons).
The nucleus combines protons and neutrons. Because the neutron has no charge, the nucleus has a net positive charge from the protons alone.
Atomic number = number of protons
The atomic number of an element is the number of protons in the nucleus.
- Oxygen: 8 protons → atomic number 8.
- Copper: 29 protons → atomic number 29.
Change the proton count and you change the element. Neutrons can vary (isotopes), but the atomic number is the identity card of the element.
Electrons are much smaller and lighter
Review questions in the textbook stress scale:
- An electron is enormously smaller than a proton.
- A proton weighs on the order of 1836 times more than an electron.
You will never weigh an electron on a job site. You will explain to a helper why current is about electron movement, not moving protons in the wire.
The Bohr model: shells around the nucleus
Electrons do not float randomly. In the introductory model, they occupy shells (energy levels) around the nucleus.
Think of shells as parking levels:
- Inner shells are closer to the nucleus.
- Outer shells hold valence electrons — the ones that participate in bonding and conduction.
The outer shell is where chemistry and electricity meet. Conductors, insulators, and semiconductors differ mainly by how many valence electrons they have and how tightly they are held.
Matter, elements, and compounds
An atom is the smallest part of an element (pure substance).
A molecule is the smallest part of a compound. Water (H₂O) is a compound: two hydrogen atoms plus one oxygen atom sharing electrons to reach a stable outer shell of eight.
Do not confuse atoms with molecules. Copper wire is elemental copper atoms in a metallic structure. PVC insulation is a compound.
Why the electrician cares about structure
You do not need nuclear physics on a service call. You do need to know:
- Current is movement of electrons, not protons.
- Materials behave differently because of valence electrons (next lessons).
- Heat appears when electrons move through resistance — linked to valence-shell interactions.
When a helper asks “what is electricity made of?” you should answer without hand-waving: charged particles; in circuits, mainly electron flow in conductors.
Field case
Situation. A new helper points at a copper conductor and asks: “Is electricity the copper moving through the wire?”
How to think with this lesson.
- The copper atoms stay in place in solid wire.
- What moves are free electrons in the conductor’s structure.
- Protons are locked in the nucleus; they define the metal but do not drift down the circuit.
Lead answer: “The wire is the highway. The cars are electrons. The road doesn’t drive to the house — the cars do.”
Learning conclusion: atomic structure explains what can move; the next lessons explain charge, materials, and units.
In the field
Symptom
Confusion about what actually moves in a wire
Where to look
Lesson model: nucleus vs shells; conductor vs insulator (upcoming)
Likely causes
- Treating “electricity” as a fluid or as atoms sliding
- skipping particle charges
What to measure
- Can the learner name the three particles and their charges?
What not to do
- Skip straight to formulas without particle/charge foundation
Checklist
- I can name proton, electron, neutron and their charges
- I know atomic number equals number of protons
- I can contrast hydrogen and helium at a simple level
- I understand electrons are far lighter than protons
- I know atoms (elements) differ from molecules (compounds)