What is an Atom and How Do We Know?

Introduction to Atoms

• Atoms are the fundamental building blocks of chemistry.
• Scientists have discovered 118 kinds of atoms, known as elements, displayed on the periodic table.
• Atoms comprise everything from electronic screens to human eyes.
• A single atom is so small it can't be seen with the naked eye.

Historical Perspective on Atoms

Ancient Greece

• Democritus:
  • Proposed that matter consists of small, indestructible particles called atoms (atomos = uncuttable).
  • Lacked evidence for his claims, leading to their dismissal by many.

Arabic Alchemy

• Jabir ibn Hayyan:
  • Advanced methods of extracting pure substances from crude materials via filtration, boiling, and cooling.

1700s: Chemical Elements

• Antoine and Marianne Lavoisier:
  • Studied pure substances and found some could be broken further, like water into hydrogen and oxygen.
  • Introduced the concept of elements - substances that cannot be broken down further.

Development of Atomic Theory

John Dalton (Early 1800s)

• Discovered that elements combine in small, whole-number ratios.
• Suggested elements are made of indivisible units (atoms).
• Published findings in a 560-page book with illustrative drawings.

Confirmation of Atoms

• Albert Einstein (1905):
  • Proposed experiments and equations to confirm atom existence and size.
• Jean Perrin:
  • Conducted experiments validating the existence of atoms.

Visualizing Atoms

Scanning Tunneling Microscope

• Developed in the 1970s by Gerd Binnig and Heinrich Rohrer.
• Uses electron tunneling to "feel" the surface of samples.
• Produces images of atoms, for example, silicon atoms.

Advances in Atomic Imaging

• Dr. Ara Apkarian's Team:
  • Modified scanning tunneling microscope to use light to see atoms.
  • Captured images of a single nitrogen atom.

Summary

• Atoms are fundamental and essentially indestructible components of chemistry.
• Their existence is confirmed through chemical reactions, mathematical equations, and new imaging technologies.

Next Steps

• Explore the structure within atoms in upcoming animations.

Additional Resources

• CASEL Research Center: Involved in atomic and molecular imaging and outreach.
• Bond Breaker Video Game: Teaches basics of chemistry and nuclear physics.
• Support through Patreon is appreciated.

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