The Atomic Nature of Matter

The Physics Hypertextbook™
© 1998-2008 by Glenn Elert -- A Work in Progress
All Rights Reserved -- Fair Use Encouraged

prev | up | next

---

Discussion

Everything goes somewhere. Nothing disappears -- Beakman.

The idea of atoms is very old. Very, very, very old -- well, maybe only very, very old.

Water would not move from place to place if it were not that it seeks the lowest level and by a natural consequence it never can return to a height like that of the place where it first on issuing from the mountain came to light. And that portion of the sea which, in your vain imagining, you say was so high that it flowed over the summits of the high mountains, for so many centuries would be swallowed up and poured out again through the issue from these mountains. You can well imagine that all the time that Tigris and Euphrates have flowed from the summits of the mountains of Armenia, it must be believed that all the water of the ocean has passed very many times through these mouths. And do you not believe that the Nile must have sent more water into the sea than at present exists of all the element of water? Undoubtedly, yes. And if all this water had fallen away from this body of the earth, this terrestrial machine would long since have been without water. Whence we may conclude that the water goes from the rivers to the sea, and from the sea to the rivers, thus constantly circulating and returning, and that all the sea and the rivers have passed through the mouth of the Nile an infinite number of times.
The Notebooks of Leonardo da Vinci. edited by Jean Paul Richter, 1880

A physicist is the atoms' way of thinking about atoms.
Anonymous

The evidence for atoms is not that old.

Chemistry

• Laws of definite and multiple proportions
• Periodic Table: Mendeleev predicted three new elements:
  1. "Ekaboron", atomic mass = 44;
  2. "Ekaaluminum", atomic mass = 68, density = 5.9 g/cm³; and
  3. "Ekasilicon", atomic mass = 72, density = 5.5 g/cm³.

Gas laws are indirect evidence for atoms?

Einstein's paper on Brownian motion

Any other evidence?

Summary

• Ordinary matter (as opposed to dark matter) is mostly composed of atoms.
• Atoms …
  • are discrete entities.
    • A discrete system is composed of distinct individual parts. A discrete system is separable into pieces.
    • The opposite of discrete is continuous. A continuous system forms an unbroken whole without interruption. One region blends seamlessly into another.
  • can only be found in a limited number of basic types called elements (short for chemical elements).
    • There are 90 naturally occurring elements found on earth.
    • An additional 28 elements have been produced artificially in laboratories on earth.
    • A few elements that exist on earth only in the laboratory have been detected in stars other than the sun.
  • can be stable or unstable.
    • Unstable atoms have a finite lifetime.
      • There is a statistical probability that an unstable atom will decay into an atom of a different element.
    • Stable atoms are eternal.
      • The stable atoms of everyday existence are several billion years old.
        • Nearly all of the hydrogen and helium in the universe was created in the first three minutes of the universe's existence (13.7 billion years ago).
        • Nearly all of the elements heavier than helium found on the earth were created many millions of years before the solar system formed (4.5 billion years ago).
      • Stable atoms can be used over and over again (recycled) in different combinations and will never "wear out".
  • can be "seen" only with great difficulty.
    • Atoms are effectively "invisible".
      • Atoms are on the order of 10⁻¹⁰ m in size.
      • Light waves are on the order of 10⁻⁶ m in size.
      • Since light is 10,000 times larger than atoms, atoms are too small to be "seen" with light. (No optical device can ever be used to image atoms.)
    • Atoms can be inferred to exist through …
      • the chemical laws of definite and multiple proportions.
      • the physical laws of statistical thermodynamics.
    • Atoms can be imaged through …
      • x-ray diffraction
      • scanning tunneling electron microscopy
      • atomic force microscopy
• Atoms can combine to form …
  • ionic solids
  • network solids
  • metallic solids
  • molecules

Problems

practice

1. Write something.
   • Answer it.
2. Write something else.
   • Answer it.
3. Write something different.
   • Answer it.
4. Write something completely different.
   • Answer it.

numerical

1. problems

Resources

• general
  • The Mechanical Universe and Beyond (video on demand, login required)
    • The Atom, A history of the atom, from the ancient Greeks to the early 20th century, and a new challenge for the world of physics.
• nanotechnology
  • World's Smallest Abacus, IBM, Zurich

---

prev | up | next

Another quality webpage by Glenn Elert

home | contact bent | chaos | eworld | facts | physics