Periodic Table of the Chemical Elements Inquiry
Mendeleyev's Wonderful Discovery of Elemental Atomic Relationships
Aug 11, 2009
Approximately 99% of the earth is composed of just 10 of the 92 naturally-occurring elements. Elements are the basic stuff of matter and life, and these elements are what scientists study. Dmitri Mendeleyev, a Russian scientist, in 1869, introduced his Periodic Table of the elements to provide a better understanding of the elements and their interrelations.
The World of Elements is Varied and Includes Metals and Non-Metals, Gasses and Solids
Scientists were discovering and characterizing elements from the 1700s onward. Along the way scientists tried to make sense of the accumulating and large variety of elements. There were: gold, silver, iron, lead, mercury, carbon, arsenic, tin, antimony, and prosaic elements like hydrogen, oxygen, nitrogen, potassium, sodium, phosphorous, sulfur, and noble gasses like neon, argon, xenon. Each element had distinct properties and features. Some elements seemed related to other elements, and some were very different. It was a literal chemical zoo and menagerie — all caged together in assorted jars, bottles, flasks and metal containers — waiting for the next experiments.
Today, 92 naturally-occurring elements are known. Mendeleyev gave chemists unique "elemental" insights and understandings with his Periodic Table of the Elements that even predicted some undiscovered elements (See "Table" photos below. Double click to enlarge for great information).
Mendeleyev's Periodic Table of Elements
Mendeleyev enjoyed playing cards — at least the chemical cards that he prepared, one for of each element. On each card he wrote the element's name and symbol, and its atomic mass (weight). Each card also denoted characteristics such as: metal, or metal-like, or non-metal. Then he played his card game. Mendeleyev moved and arranged his cards sequentially by weights, progressing from the left to right, and he created vertical columns along the way. Occasionally, he shifted a weight card forward to better fit the elements in a vertical row that connected familial, chemical features. For example, he shifted tellurium, 127.6, ahead of iodine, 126.9, because tellurium matched up better chemically with sulfur and selenium, and iodone matched better with chlorine and bromine. It was a clear, logical and intuitive mind at work, and it was the mark of great science!
The Periodic Table Merits Careful Study
It has 18 vertical groups and 7 horizontal rows called periods. Each element has a symbol. In many cases a single letter, or at most two letters, are used. Often the letters indicate the beginning letter of the element's name. In the first vertical column note: H = hydrogen, Li = lithium, Rb = rubidium, Cs= cesium, Fr = franconium are related. Notice, also, that both sodium = Na and potassium = K have letters that represent the first letter of the Latin names "natrium" and "kalium" respectively, for these two elements.
Mendeleyev arranged the elements in a weighted and logical order as he critically thought out the properties, similarities and differences of all those elements. The Periodic Table shows the atomic number (= number of protons) at the top of the element's symbol, and the atomic weight (number of protons and neutrons) at the bottom. In two photos below, in this article, find hydrogen and carbon atoms. Hydrogen has a single proton and no neutrons, carbon has 6 protons and neutrons. The protons and neutrons each are assigned a weight of one. Thus, hydrogen has an atomic mass of one and carbon has a mass of 12. Also, each atom has the same number of electrons as protons.This gives the atom a neutral charge. Note: electrons are light and add no mass to the atom.
As one goes from left to right, or top to bottom in the Periodic Table both atomic number and mass increase. Thanks to Mendeleyev all know the elements better!
Read more about atoms and the chemical bonds of atoms.
Sources
Hill, J.W. and D.K. Kolb. 1995. Chemistry for Changing Times. Prentice-Hall Inc., Engelwood Cliffs, N.J.
 |
 |
 |
 |
 |
