Chemistry of Gems and the Periodic Table

There are currently 110 elements recognised by the International Union of Pure Applied Chemistry (IUPAC). These elements are displayed in the form of a matrix called the Periodic Table. The current form of the Periodic Table, including the new group numbers (1-18), was agreed to by the IUPAC in 1985.

The periodic table is the most important chemistry reference available. It arranges all the known elements in an informative array. Elements are arranged left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass.

All minerals, therefore gems, are made up of elements. Some minerals have a simple chemistry with just one or two elements, such as Diamond which consists only of Carbon [C] or Quartz consisting of Silicon Dioxide [SiO₂]. Others, such as Tourmaline [NaLi_2.5Al_6.5(BO₃)₃O₁₈(OH)₄] or Axinite [(Ca, Mn, Fe, Mg)₃Al₂BSi₄O₁₅(OH)], are very complex and may vary in chemical composition from one crystal to another. The properties of a gem are determined by and affected by its chemical composition. These properties are things like crystalline structure, crystal shape, optical properties, cleavage, hardness and color.

While some of these properties are not immediately evident when looking at a gem, color is very obvious. The beautiful rose-pink to orange-red colors of a Rhodochrosite gem are due to its manganese (Mn) content. A Demantoid Garnet is colored deep green by its chromium (Cr) content. Gems from the Beryl family all have the same basic chemistry but are different colors due to the various trace elements added. Aquamarine gets its blue-green color from traces of ferrous iron (Fe). Bixbite (red Beryl) is colored red by manganese (Mn). Emerald is colored green by the addition of chromium (Cr). Heliodor is yellow from ferric iron (Fe). The pink variety of Beryl, Morganite, gets its color from slight amounts of manganese (Mn). Goshenite however, is colorless because it is pure Beryl and not colored by any impurities.

The Periodic Table

Russian chemist Dmitri Ivanovich Mendeleev (1834-1907) developed his Perodic Law and the Periodic Table in 1869 by putting the 63 elements he knew in order by atomic weight and chemical valency. Since then others have tried to improve on this method, but Mendeleev's Periodic Table has proven to be the best.

The term "periodic" came from the regular occurance of certain chemical properties in the list of known elements when these are arranged in order of increasing relative mass. According to Mendeleev: "The elements, if arranged according to their atomic weights, exhibit an appartent periodicity of properties."

How to read the Periodic Table

Each Element is represented by a number and a letter symbol in a colored box. The top number is the Atomic Number. The one or two letters in the middle represent the Atomic Symbol. The number at the bottom is the Atomic Weight. The color in the box indicates the type of element: metals, metaloids, non-metals, gases, etc. The color of the Atomic Symbol letters indicates the physical state of the element.

25
Mn
54.94

- Atomic Number
- Atomic Symbol
- Atomic Weight

(hold your cursor over the atomic symbol for more information or click on the atomic symbol for a new window with more detailed information)

Atomic Number
The number of protons in an atom defines what element it is. For example, hydrogen atoms have one proton, carbon atoms have six protons and oxygen atoms have eight. Each element has a unique number of protons. No two elements have the same number of protons, therefore each element has a unique atomic number. The number of protons in an atom is referred to as the atomic number of that element. The number of protons in an atom also determines the chemical behavior of the element.

Atomic Symbol
The atomic symbol is one or two letters chosen to represent an element ("H" for "hydrogen", etc.). These symbols are used internationally. Typically, a symbol is the truncated name of the element or the truncated Latin name of the element. The colors of the atomic symbols were chosen by us for purposes of clarity and not part of the format of the Periodic Table. Atomic symbol colors are further explained below in "State of the Element".

Atomic Weight
The atomic weight is the ratio of the average mass of a chemical element's atoms to a standard. Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12. An isotope is one of two or more species of atoms of the same chemical element that have differenct atomic mass numbers (protons + neutrons). The atomic weight of carbon is 12.0107, which is the average that reflects the typical ratio of natrual abundances of its isotopes.

The concept of atomic weight is fundamental to chemistry, because most chemical reactions take place in accordance with simple numerical relationships among atoms. Since it is almost always impossible to count the atoms involved directly, chemists measure reactants and products by weighing them and reach their conclusions through calculations involving atomic weights.

Periods and Groups
Periods are arranged horizontally across the Periodic Table. Each row is referred to as a Period. There are 7 Periods. The elements in a Period have the same number of valence shells. All elements in the same row tend to have their valence electrons in the same energy level. For example in Period 4, potassium (K), vanadium (V), germanium (Ge) and bromine (Br) all have their valence electrons in the fourth energy level (4th shell).

Each column is referred to as a Group. There are 18 Groups. In each Group the elements of that group tend to have the same number electrons in their outer most shell, (valence shell). Elements in Group 17, such as fluorine (F), chlorine (Cl) and bromine (Br), have seven valence electrons, elements in Group 13 have three valence electrons and so on.

State of the Element
The colors of the letters of the atomic symbol indicates the physical state of the element: black for solids; blue for liquids; red for gases; fuchsia for synthetics. The colors of the atomic symbols were chosen by us for purposes of clarity and not part of the format of the Periodic Table.
 

Mn

Solid

Br

Liquid

He

Gas

Tc

 Synthetic

(black letters)

(blue letters)

(red letters)

(fuchsia letters)

Types of Elements
The color of the box for each element indicates the type of element: metals, metaloids, non-metals, gases, etc. The colors of the boxes were chosen by us for purposes of clarity and not part of the format of the Periodic Table.

Alkali Metals

Metaloids

Alkaline Earth Metals

Non-Metals

Transition Metals

Halogens (non-metals)

Other metals

Nobel (inert) Gases (non-metals)

Lanthanides - Rare Earth Metals

Elements currently under review by the IUPAC

Actinides - Rare Earth Metals

Elements not recognised by the IUPAC

Summary
The Periodic Table contains valuable information about all known atoms responsible for matter in our universe. The table can be thought of as a map in which information about physical characteristics and chemical behavior can be found. The table also organizes the elements in such a way that trends in chemical behavior and physical properties can be realized.

More information
To view more information about a particular element, hold (do not click) your cursor over the letter symbol of the element you want information about. Basic information will be displayed in a small data window. If you would like more detailed information, click on the letter symbol and a new window will open with information about that element.

The source for detailed information pages that we link to is from the University of California, the US Department of Energy and the Los Alamos National Laboratory and is copyrighted by the Chemistry Operations at the University of California and the Los Alamos National Laboratory Chemistry Division.

Periodic Table of the Elements

Hold your cursor over an atomic symbol for more information or click on the atomic symbol for a new window to open with more detailed information.

"Refrain from illusions, insist on work and not on words.
Patiently search divine and scientific truth."

The dying words of Dmitri Mendeleev's mother Maria to her son.