One of the main ways forensic scientists and chemists analyze the data they collect is using a piece of equipment called a spectrometer. You will be using several different types of spectrometers in your murder investigation so it will be important for you to understand how this piece of equipment works. But to understand this you will need some background information first, starting with the structure of the atom.
The development of what we understand as the structure of the atom today started long ago. In the 5th century B.C. a philosopher named Democritus hypothesized that all matter (plus space and time) is composed of tiny indestructible units, called atoms.
Unfortunately for us, Aristotle, who was a much more popular philosopher at the time, disagreed with Democritus’ theory and thus the development of good atomic theory was set back by a couple of millennia. But eventually Democritus' theory was rediscovered in a poem by the Roman poet Lucretius in 1417. In Democritus' theory, the atoms remain unchanged when reacted, but moved about in space to combine in various ways to form all macroscopic objects. It is really amazing how close he got to the truth just by thinking it through.
Atomic Structure
RicochetScience (YouTube)
Unfortunately, it took roughly 400 years more for modern atomic theory to reemerge. John Dalton began the theory with the following set of postulates.
- All matter is made of atoms. Atoms are indivisible and indestructible.
- All atoms of a given element are identical in mass and properties.
- Compounds are formed by a combination of two or more different kinds of atoms.
- A chemical reaction is a rearrangement of atoms.
Looking at the postulates one by one there is both correct and incorrect aspects to each statement.
- Atoms are not indivisible or indestructible. The invention of the atomic bomb proves this postulate false. But in the normal course of events (barring grandiose explosions) atoms remain together.
- While all atoms of a given element do have the same number of protons which gives them a great deal of their chemical character, they can vary in their mass and properties by changes in their number of neutrons and electrons. So again there is both truth and mistakes in the second postulate.
- The third and fourth postulates are where Dalton really got it right. Compounds are formed by the combination of atoms and a chemical reaction does lead to the rearrangement of atoms so these two postulates were dead on.
Now that we know that all matter is composed of atoms, the next logical question to ask is "what is an atom made of?"
Atomic Structure is fairly simple. It is often described as similar to the solar system with the nucleus representing the sun and the electrons acting as the planets:
The atom is composed of three types of particles located in two areas:
The protons and neutrons are located in the nucleus and the electrons are located in energy levels surrounding the nucleus.
