Elements That Occur in Nature

The Debate

• As of May 2011, periodictable.com lists 118 known elements. Out of these, about 88 to 94 occur naturally, depending on which expert you ask. Dr. James B. Calvert, an Associate Professor Emeritus of Engineering in the University of Denver, claims that "There are only 88 naturally-occurring chemical elements. The elements 43, 61, 85 and 87 have no stable isotopes, and none of long half-life, so they are not naturally present."

  Although Dr. Calvert's argument rings true, the most widely accepted number of naturally occurring elements is 92, with elements 43 (technetium), 61 (promethium), 85 (astatine) and 87 (francium) considered naturally occurring.

Types of Naturally Occurring Elements

• The accepted naturally occurring elements are numbers one to 92 on the periodic table. These 92 elements have four major types: metals, nonmetals, metalloids and transition metals.

  Metals and transition metals are malleable, excellent conductors of electricity and heat, and solid at room temperature (mercury notwithstanding). The nonmetal group conducts electricity poorly and exists in solid, gas or liquid form at room temperature. Lastly, metalloids border the line between nonmetal and metal elements, having some properties of both.

Stability

• Elements one to 40 on the periodic table have stable isotopes, most of which are nonradioactive and won't decay. Elements 41 to 82, except for promethium and technetium, are "metastable" but may be prone to decay and may also be radioactive. Metastable elements are believed to have very long decay rates, not verifiable by laboratory testing. The remaining naturally occurring elements -- elements 83 to 92 -- are unstable and radioactive. Unlike the other groups, scientists can measure the decay rates.

Abundance in Nature

• The abundance -- or dearth -- of an element in nature is the major reason why there is a disagreement on the exact number of naturally occurring elements. Out of the 92 elements accepted to be naturally occurring, technetium, promethium, astatine and francium are scarce and decay very quickly. All four elements are radioactive and can only be found in very small amounts in certain uranium ores.

  Neptunium and plutonium -- considered man-made elements -- are also found only in trace amounts in rare and special ores of uranium and radium. If these two elements are accepted in the naturally occurring category, the total number of naturally occurring elements reaches 94.