Scientists use two methods to see atoms

Students in Katherine Crawford's fifth-grade class at West Oak Middle School asked: "How can scientists see atoms?"

Atoms are extremely small - 1 million times smaller than the thickest human hair - according The Physics Factbook.

"There are some fundamental rules scientists apply to map atoms, but there's no technology to see atoms with your eyes," said Assistant Chemistry Professor Andy Kidwell of Harper College in Palatine.

An atom, taken from the Greek word that means "unable to be divided," is the most basic element of all things. Everything is made up of atoms. Atoms have even smaller components, called protons, neutrons and electrons. A molecule of water contains two hydrogen atoms and one oxygen atom.

The Ancient Greeks suspected that atoms existed, but it wasn't until the 1700s and early 1800s that scientists like Lavoisier, Dalton, Proust and Avogadro developed basic theories that began the science of chemistry began.

In the 1800s, Dmitri Mendeleev arranged all known elements in a chart called the Periodic Table of the Elements. Even though all the elements had not yet been discovered, he determined that elements could be organized by weight and chemical property. This organization was a major advancement in science.

Say we want to find out what something is made of. There's no microscope or apparatus that lets us take a direct peek inside to see what kinds of atoms are present. Chemists have many tools to study atoms but they use two primary methods to learn about the arrangement of atoms, crystallography and scanning tunneling microscopy, simply called STM.

Professor Kidwell says these techniques are similar to looking at Earth from outer space. "If we lived in outer space and we were looking at Earth, we would see roads and structures, but the people would be too small to see with the naked eye. Similarly, we do not observe electrons, protons and neutrons. Instead we observe characteristics they exhibit."

Crystallography uses x-ray light to shine on a crystal.

"In a crystal structure, the molecules or atoms have an organized, rigid arrangement," Professor Kidwell said. As light is diffracted from the atoms, a pattern is created. Chemists use this pattern to determine what atoms exist in the crystal.

This year two scientists were awarded Nobel Prizes for charged-couple device (CCD) technology, which greatly improved x-ray crystallography.

The second method used to "see" atoms is STM. The process uses an extremely sharp tip to scan a surface. The tip is charged with electricity.

"Because the tip is so pointed, it can measure electron clouds," Professor Kidwell said. The electricity in the sharp point is repelled from the atom's electron cloud, the area that surround an atom's nucleus.

Even though chemists can't see atoms, the tools they use to measure their existence helps to find out important information, like how to adjust car emissions so air quality improves.

"For example, we could measure atoms on the surfaces of a car's catalytic converter to help make that process work more efficiently." Professor Kidwell said.