Chemistry

Study of matter, its properties, and the changes it undergoes.

What is Matter?Physical and Chemical PropertiesChanges in Matter
Atomic StructureThe Periodic TableChemical Reactions and Equations
Chemistry in the KitchenChemistry in the EnvironmentMedicine and Materials
Mastering VocabularySolving Chemistry ProblemsMaking Connections
What is Matter?Physical and Chemica...Changes in MatterAtomic StructureThe Periodic TableChemical Reactions a...Chemistry in the Kit...Chemistry in the Env...Medicine and Materia...Mastering VocabularySolving Chemistry Pr...Making Connections
Advanced Topics

Atomic Structure

Peeking Inside the Atom

Atoms are made up of even smaller particles called protons, neutrons, and electrons.

  • Protons have a positive charge and are found in the atom's center, called the nucleus.
  • Neutrons have no charge (they're neutral) and are also in the nucleus.
  • Electrons are negatively charged and whiz around the nucleus in regions called electron shells.

The number of protons determines what element an atom is. For example, hydrogen has 1 proton, while oxygen has 8.

Atomic Number and Mass Number

  • Atomic number: Number of protons in an atom.
  • Mass number: Number of protons plus neutrons.

Why Does the Structure Matter?

The arrangement of electrons affects how atoms join together to form molecules. The atomic structure explains why elements react in certain ways and helps us create new materials.

Key Formula

\[Atomic Number = Number\ of\ Protons\]

Examples

  • Carbon atoms have 6 protons, 6 neutrons, and 6 electrons.

  • Helium's full outer shell makes it very stable and unreactive.

In a Nutshell

Atoms are made up of protons, neutrons, and electrons, and their arrangement explains chemical behavior.

Key Terms

Proton
A positively charged particle in the nucleus of an atom.
Neutron
A neutral particle in the nucleus of an atom.
Electron
A negatively charged particle that orbits the nucleus.
Nucleus
The center of an atom, containing protons and neutrons.
Atomic Number
The number of protons in an atom, which determines the element.
Next
The Periodic Table