What Are Protons, Neutrons, and Electrons?
Every atom is built from three fundamental particles: protons and neutrons in the nucleus, and electrons orbiting around them. These particles differ in charge, mass, and location.
Protons carry positive charge, neutrons carry no charge, and electrons carry negative charge. Protons and neutrons cluster in the nucleus; electrons orbit at large distances.
- •Positive charge (+)
- •Mass ≈ 1 amu
- •Located in nucleus
- •Symbol: p⁺
- •No charge (0)
- •Mass ≈ 1 amu
- •Located in nucleus
- •Symbol: n⁰
Step-by-step worked examples
A hydrogen atom has 1 proton. How many neutrons and electrons does it have?
Hydrogen-1: 1 proton, 0 neutrons, 1 electron (to balance charge)
An oxygen atom has 8 protons. How many electrons does a neutral oxygen atom have?
Neutral atoms have equal protons and electrons. Oxygen: 8 protons, 8 electrons, 8 neutrons (Oxygen-16)
A helium nucleus contains 2 protons and 2 neutrons. How many electrons orbit it?
A neutral helium atom has 2 electrons to balance the 2 protons.
Flashcards
Quick quiz
Q1.A neutral atom has 6 protons. How many electrons?
Q2.Which particle is in the nucleus?
Q3.Electrons are much lighter than protons. How much lighter?
Q4.Which particles define the element?
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Common mistakes
Electrons are in the nucleus. — Correct: Electrons orbit the nucleus; protons and neutrons are in the nucleus.
Protons and neutrons have the same mass as electrons. — Correct: Protons and neutrons are ~1836× heavier than electrons.
Neutrons have a negative charge. — Correct: Neutrons are neutral (no charge).
The number of electrons and protons can be different in a neutral atom. — Correct: In neutral atoms, they are always equal.
FAQ
What are the three particles in an atom?
Protons (positive, nucleus), neutrons (neutral, nucleus), and electrons (negative, orbits).
Why is the nucleus so dense?
Protons and neutrons are packed tightly together; electrons are far away in comparison.
What determines the element?
The number of protons (atomic number Z) uniquely identifies each element.
Can atoms have different numbers of electrons and protons?
Yes — ions have unequal numbers. A neutral atom always has equal numbers.