<-CHM151 Home Page

Classifying: Calm the Chaos
A History of the Periodic Table

Chaos, The Ride:

This ride is called Chaos. It's an appropriate name. On the ride, a swirl of images confuses the mind. There's just too many things that you are trying to take in.

Chaos in Life:

There's a movie called chaos. and from their poster is appears to focus on the chaos of life. We can all relate to this. Too many things to grasp and get control of.

Chaos in the Cosmos:

The subtitle says, "The Stunning Complexity of the Universe." Yes, complexity can lead to chaos. Humans are normally uncomfortable with chaos and complexity. They want to simplify it.

One type of complexity is figuring out what everything in the world is made of. For example, are stars, clouds, mountains, rivers, animals, and plants made from something different? Even on an animal, is the horn, teeth, fur, eyes, muscles made from different materials? Is there a way to simplify what millions of things are made of?

Water is the Only Element:

Around 600 B.C., the Greek philosopher, Thales, proposed that all things are made from water. It seemed logical. Water is very abundant. Also, all living things consumed water. So maybe water was being transformed into different shapes and different materials. This belief would really simplify things.

Water and Earth:

Around 500 BC Xenophanes suggested that everything was made from water and earth. Plants needed both water and soil to grow. Animals ate the plants, so they, too, were made from water and earth.


Four Elements:

Around 440 BC Empedocles suggested that there were four elements: Water, Earth, Air, and Fire. It seemed logical because when things caught fire moisture is released, air can be felt coming up from it, and the ashes show the earth that it contained. Classifying all matter as only being made of four elements certainly calmed the chaos of the world.

Around 400 BC another Greek philosopher, Democritus, agreed there were four elements but he proposed that there was a limit to how small an element could be divided.
For example, he said matter may look smooth and solid, but if we could see it very, very close, then we would see that it's made of pieces. An analogy is a beach looks smooth from a distance, but up close we know it's made up of grains of sand.
Again, he proposed that elements were composed of very small pieces that could no not be divided. He called these pieces Atoms after the Greek word for Indivisible.

The 5th Element:

Around 340 BC Aristotle said he didn't believe in the theory of Atoms because you are putting a restriction on the gods. If the gods wanted to divide an element to something smaller than an atom, they could.

Aristotle also said the Sun, Moon, & Stars (and all heavenly bodies) were made from a fifth element. This element was so perfect that in contact with base (low value) metals, the fifth element could turn that metal into gold. The fifth element could also cure people and keep them young. This started a 2,000 year hunt for a nonexistent element. So this rather spiritual element didn't really help combat chaos because no one ever found it.

There was even a problem with the other four elements.

The idea of an element is that it is a building block for other things. An element is not supposed to be made from smaller building blocks.

Antoine Lavoisier was a nobleman from France who lived in the 1700's (His wife, Marie, was his assistant).   Lavoisier discovered that water is made from hydrogen and oxygen and that air is made from oxygen and nitrogen. So water and air can't be elements because they are built from something simpler. So it was decided that if a substance can be decomposed, then it is not an element.

By the way, Lavoisier is often considered the Father of Modern Chemistry. He wrote the first modern textbook on chemistry.


These were the agreed upon elements at the time of Lavoisier. The names in the right purple column were listed as elements but Lavoisier suspected that they weren't elements; he just couldn't get them to decompose. Later, lime was shown to be calcium combined with oxygen. Magnesia consisted of magnesium, sulfur and oxygen. Silex and Argill were also found not to be elements but made up of true elements.


An important point to make here is that science wishes to find the fundamental principles that explain the complexity around us, but it won't stay with a simple view if it finds evidence that requires more explanation. In other words, chemistry didn't stick with these five elements even though it was simple because experiments showed that there were more elements and these were not elements.

Chemistry looks to identify the simple building blocks and fundamental forces, but at the same time it won't ignore evidence that suggests something more complex is going on. So we are always looking for simple explanations but not so simple they can't explain our observations.

In the late 1700's John Dalton from England resurrected Democritus' idea of atoms. For example, this gold bar can only be divided to the point that you end up with pieces (spheres) of gold that can no longer be divided, in other words, they were atoms of gold.

The next idea would tremendously simplify the complexity of all the materials around us. Dalton suggested that substances around us were made up from a grouping of specific number of atoms of different elements. For example, a water molecule is made from two atoms of hydrogen and one atom of oxygen (upper right). If there's 2 oxygen atoms and 2 hydrogen atoms (lower right) then it's not water but something else (hydrogen peroxide). Salt is made from one sodium atom and one chlorine atom. Ammonia is made from 3 hydrogen atoms and one nitrogen atoms (lower left).

In other words, we might see a lot of items around us, there's just a handful of elements that have combined to make up what we see. For example, here carbon, hydrogen, nitrogen, and oxygen molecules make up most of the people, foods, and plastics. Aluminum and iron for the metal objects. Silicon and oxygen for the glass.

At the time of Dalton, these were the elements and the symbols that was used to represent them. The numbers are their relative weights. Azote was the name for nitrogen. It was considered 5 times heavier than hydrogen. That was incorrect because they didn't realize that hydrogen went around in pairs.

Notice the symbols for iron, silver, and gold use the letters I, S, and Gold. That was going to change because of a chemist that was doing a better job at measuring the relative masses of elements.

Johan Jacob Berzelius from Sweden had done 2000 experiments to determine accurate relative masses for the know elements. That apparently gave him the honor of making up the below rules.

Older elements take the symbol from their Latin name.

Fe from Latin word for iron, Ferrum.
Au from Latin word for gold, Aurum.
Ag for Latin word for silver, Argentum.

Elements discovered in recent times would use symbols based on English name. For example, O for Oxygen.

Researchers had already began to arrange and classify elements in the following ways:

Metals vs. nonmetals

Tables of increasing atomic weight
(like you've seen above)

John Newlands from England had a different way to arrange elements. It was based on his love of music.


On the left the elements, Lithium, Beryllium, Boron, etc. are listed from lightest to heaviest. Newlands noticed lithium(Li), sodium (Na), and potassium(K) all react violently with water and they were 8 apart on the list. Then he noticed fluorine, chlorine, and bromine were all very corrosive and formed acids. They were also 8 apart on the list. Coincidence?
It was like octaves in music. Starting with the "A" note, after 8 notes, the "A" note repeats. So instead of a long list, he arranged them in three columns. Amazingly, the elements in each row had similar properties with each other. This indicated some hidden connection between the elements in each row that would simplify our understanding of this list. Unfortunately, when Newlands presented this to the Royal Chemistry Society, they laughed at him and told him if he had to rearrange the elements, try alphabetizing.

Mendeleev portrait Meanwhile, Dmitri Mendeleev in Russia had noticed the same interesting pattern. There seemed to be a periodic reappearance of properties. For many elements, the pattern repeated after every eight elements.
old periodic table This is Mendeleev's first Periodic Table. Notice he also has lithium, sodium, and potassium in the same row. Again, it's because they have the same properties. He also have fluorine, chlorine, bromine, and iodine in the same row. Like Newlands, he also had unknown elements positioned after aluminum(Al) and Silicon(Si). Since chemists paid attention to Mendeleev they looked for the unknown elements knowing that one would be similar to boron(B) and aluminum(Al) and the other would be similar to carbon(C) and silicon(Si) because they were in the same row (group). Sure enough within two years the new elements, gallium and germanium were discovered.
Stone Periodic table

Here is Mendeleev's Periodic Table of the Elements carved in Stone. In this later version, the elements that are related are placed above and below each other like the modern versions of the Periodic Table.

4 elements to modern periodic table In a couple of thousand of years, we see that we came a long ways. At first, we oversimplified the chaos of the world with only 4 elements. Now we realize that there's about 100 elements. 100 is a lot more, but that's a lot less than the millions of different materials we see in nature. So we have simplified the chaos of the world. Furthermore, the 100 elements are simplified by the grouping of elements in the arrangement seen on the modern Periodic Table. This form of classifying reduces the idea of 100 separate elements to about the 8 groupings.
Periodic Table

Again, the Periodic Table of the Element has the elements listed by increasing mass but grouped by similar reoccurring (periodic) properties. Some groups are in columns and some are in rows. Let's explain the logic behind these groupings.


Metals vs. non-metals The simplest grouping indicated on the Periodic Table is to divide the elements into metals and nonmetals. Here the green stair step shows where they are separated.
Metal hub cap Metals are easy to spot. First of all they are shiny.
metal surface atomic level ripples This can explain why metals are shiny. This is the surface of copper at a ridiculously high magnification. The surface shows a lake of electrons along with ripples. The two islands are imperfections on the surface. Most likely caused by a couple of atoms that aren't copper.
President Bush with branding iron Another way we recognize metals are that they are good conductors of heat. That's why a branding iron is made from metal. The metal transfers quickly to the animal's hide.
non metal resisting torch Nonmetals on the other hand do not conduct heat well. The insulating tile from the Space Shuttle are made from fibers of silicon and oxygen (silica=sand).
tesla coil, gold foil, spoons

Metals also conduct electricity. Notice that the Tesla coil sparks seek out metallic objects because they conduct electricity better than the nonmetallic materials such as wood or soil.

Metals are also malleable and can be bent or hammered into various shapes.

alkali metals

The first group is on the left side of the Periodic Table. The metals in this groups are called the Alkali Metals.

What is usually never mentioned is why these metals are called "Alkali Metals."

Since I don't like to be given names without learning about the origin of that name, I will give you background on these names.

Akali saltwort plant

Al Kali is an Arabic word. "Al" means "the" in Arabic. You hear it pretty often. Think of Alcohol, Algebra, and Al Qaeda. The "Al" in all of these mean "the". Kali is Arabic for "Saltwort" plant.

The saltwort plant lives near shores of salty seas. When the saltwort (alkali) plant is burned, the ashes contain sodium hydroxide (NaOH) and potassium hydroxide (KOH). When the ashes are placed in water, the hydroxide (OH-) dissolves in the water and can neutralize acids (H+). Anything that increases the level of hydroxide (OH-) in water is called alkaline. Alkaline batteries contain KOH and it owes its name to the saltwort plant spoken in Arabic (Al Kali).

Alkali Earth Metals
The second group of the metals from the left is called "Alkaline Earth Metals". You know where the word, "Alkaline" came from. "Alkaline Earths" were the old name for oxides of certain metals. Berylia, Magnesia, Lime (Calx), Strontia, and Baryta. These oxides put in water makes the water alkaline because it releases hydroxide ions into the water. Here's the reaction:
CaO + H2O --> Ca(OH)2--> Ca2+ + 2OH-
Now lets move to the group on the right side. They call these halogens. These are the ones that gave Newlands and Mendeleev the idea of grouping them because they are so corrosive. This is how they get their name. Place these near a metal and the metal quickly turns into a salt. "Halo" means "salt" and "gen" means generator. They are salt generators. For example, place chlorine gas near sodium metal, and you instantly get sodium chloride (common table salt). Roll cursor over image to see the reaction.
The halogens are very reactive. Fluorine is the most reactive. Our atmosphere is nitrogen and oxygen, but in an atmosphere of fluorine even water and ice will burn. (roll cursor over image). To makes matters worse, when ice or water burns, it produces hydrofluoric acid and oxygen which can cause their own problems.
Candle burn In an atmosphere of fluorine gas this candle will burn down to the glass, and then the glass will burn! When the candle burns in normal air, the wax turns into carbon dioxide and water vapor. In an atmosphere of fluorine, the wax becomes carbon tetrafluoride (Freon) and hydrogen fluoride (which become hydrofluoric acid if touches water).

Nobel gases
Noble Gases: Helium-He, Neon-Ne, Argon-Ar, Krypton-Kr, Xenon- Xe, Radon-Rn

Noble Gases: The right side group is the noble gases. They were once called the Inert Gases because they were inert and didn't combine with any other elements. However, it was discovered that some could be coaxed into combining some of the very reactive elements such as the halogens.

Along the green stair-step are the metalloids. They have properties similar to metals, such as conductivity. The electronic industry takes advantage of their ability to have their conductivity turned on or off.

Periodic table orbitals

Electron Orbitals: Sometimes a Periodic Table is color-coded to show the four types of electrons that occupy the outer shell (orbit) of the element. An electron orbital is the space that the electrons travel. There's only four of types of orbitals, so this classification of the 100+ elements simplifies the table.

I will briefly go over the 4 types of orbitals below.


s orbital
s-orbitals: Group 1 and 2 are the Alkali Metals and the Alkali Earth Metals. The reason they have similar properties is that their outer electrons occupy what's called the s-orbital. These are spherical orbitals (note "s" doesn't come from spherical). The s-orbitals can only hold a maximum of two electrons, which is why there are only two columns on the left side of the Periodic Table. Take a look.
p orbitals

p-orbitals: The elements in the blue p-block above all have their outer electrons in a p-orbital. You might call the shape of p-orbitals dumbbell shape (two lobes). There are basically 3 orientations (x, y, & z axes) of the p-orbital and each can only hold 2 electrons. That's a total of 6 electrons. That's why the p-orbital block is 6 elements wide. (Scroll up to take a look)

The dumbbell shape of the p-orbital makes you think that there's two electrons there. Realize that one electron makes both of these lobes. However, two electrons can share this space, so there might be one or two there.

d orbitals

d-orbitals: The middle of the Periodic Table (d-block) is made up of a run of 10 elements. (scroll up to take a look). The reason that there are 10 elements is that there are five orientations of d-orbitals, with each one capable of holding 2 electrons (just like the s and p orbitals). So, again, there's a run of 10 elements as the d-orbitals are getting filled (They are called the transition metals).

I'm not sure how you would describe the shape of d-orbitals. Most are like a double dumbbell (4 lobes). Again, just one electron occupies all of those lobes.

f orbitals

f-orbitals: At the bottom of the Periodic Table are two rows of 14 elements (scroll up and look). There are 14 elements in each row because this is the run of elements as the f-orbitals are getting filled up. As you probably already guessed, there must be 7 f-orbitals with each capable of holding two electrons to explain why 14 elements in the row.

Again, each of these images is one electron. In an element like uranium, there are 92 electrons; 18 of those electrons occupy f-orbitals, 40 are in d-orbitals, 30 are in p-orbitals, 14 are in s-orbitals. All 92 electrons are orbiting together around the nucleus. Somehow they stay of each others way, yet get as close to the protons in the nucleus as possible.

(These beautiful images are by Mark Winter at Sheffield University. Check out his website:
http://winter.group.shef.ac.uk/orbitron/ )

4 elements to modern periodic table At first glance, the Periodic Table is quite boring looking. I even did a presentation at a conference where I suggested we should take down the Periodic Table because it looks boring and is bad publicity for chemistry. However, it took 3 thousand years to create the table. There were thousands of alchemists who searched for elements and tens of thousands of chemists and others that hunted for elements and tried to place them on this table. Many of these people poisoned themselves while trying to expand our list of elements. In addition to purifying and identifying these elements, there was countless tedious hours of lab work to find their relative masses. To top it off, the electron orbitals of these elements were discovered only the brightest minds of the 20th century could interpret the clues from the spectrum of light coming from the elements. The Periodic Table has to be the biggest investment of human physical and mental effort ever undertaken. So even if looks boring at first glance, the insight to these building blocks of nature is staggering.
The Periodic Table is an incredible collection of knowledge but how might we use it? Let's go through a real world scenario. Consider the meltdown and explosion of the Chernobyl powerplant in the Ukraine that happened in 1986. The products of nuclear fission were scattered for thousands of miles and even got to Alaska. The first report was that large amounts of radioactive isotopes of strontium, cesium, and iodine were released. A look at the Periodic Table would help assess the danger of these elements.
Periodic Table left side This is the left side of the Periodic Table. We find cesium (Cs) in group 1 (Alkali Metals) and Period 6. You may remember that all alkali metal salts are soluble. So that means this radioactive cesium will be washed out of the air with rain and dissolve in rivers and streams plus get into ground water. Also, being soluble, it will get into the body's blood stream. As All bad news. The good news, is that being a positive ion, cesium could be filtered out by devices like water softeners that trap positive ions and replace them with sodium ions.
    Now find strontium (Sr) in group 2 (alkali earth metals) period 5. Just above strontium is calcium. This is very bad news. Calcium is readily taken up in the body to build teeth and bones. Having similar chemical properties (in same group), strontium will also get absorbed by the body and deposited in bones. Normally, this is not a problem, because naturally occurring strontium (mostly strontium-88) is non-toxic and not radioactive. However, this was strontium-90, which shoots out high speed electrons (beta radiation), which will damage surrounding cells causing bone cancer and other diseases. It's like having miniature hand grenades in the body. Again, the body can't tell the difference between the stable isotope or the unstable (radioactive) isotope.
On the right side of the Periodic Table we find Iodine in group 17 (Halogens). You may remember that most halogen salts are soluble. So we have a problem with iodine getting into the water supply. Also, iodine is readily absorbed in the body because it is needed for the proper function of the thyroid gland. Again, the natural iodine-127 is not radioactive (it's stable); however, nuclear fission produced iodine-131, which decays by shooting out high speed electrons (beta particles) and gamma rays (powerful x-rays). These will destroy the thyroid.
One defense is to take potassium iodide (KI) so that the body gets plenty of natural iodine (iodine-127) and will then not try to absorb the radioactive iodine (iodine-131) from the fallout.
olives on vine

As far as classifying the makeup of the universe, we've come a long ways. Our first classification of materials was probably, "Is it edible or not."

4 elements to modern periodic table
Later philosophers wanted a deeper understanding of what the world was made of. At first it seemed to them that the four elements were all that was needed to make the world. Over the centuries, we found over a 100 elements. With about 30 being the common building blocks of what we encounter. The Periodic Table has a calming effect to anyone who has puzzled over the make-up of the world around them. The Periodic Table identifies, compares, and organizes the elemental building blocks, giving us a chance to understand a world that was once a total mystery.
chaos movie people faces
So even though chaos will always be present, like the character in Jurassic Park pointed out, there are still ways to combat chaos and that's with understanding complexity. This requires finding classifications that simplify and explain the nature of the world. For example, teeth are classified as phosphate minerals and have a hardness value much higher than protein. Another classification is Predator vs. Prey. That pretty well explains what can happen next. So much for being calm.
<-CHM151 Home Page

Number of different visitors (not just hits) since Aug, 2009