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18 March 2010

Answer to Question #1554 Submitted to "Ask the Experts"

Category: Radiation Basics — Elements

The following question was answered by an expert in the appropriate field:

How many of the elements in the periodic table are naturally occurring?

Of the first 92 elements in the periodic table, only 90 are found in nature. The two "holes" belong to the elements with atomic numbers 43 (technetium, Tc) and 61 (promethium, Pm). These two elements have only radioactive varieties (isotopes), all of which decay away in relatively short times on a geologic scale. There are no stable forms of either. Tc was first produced and detected in the laboratory in 1937 and Pm in 1945. Additional information can be found by searching on "synthetic elements." Detailed information on every element can be found on the KLB Productions Web site on Environmental Chemistry. Elements with atomic numbers greater than 92 (uranium) have also been synthesized artificially by man. More information on this subject is given on the Scientific American Ask the Experts Web site.

James Turner, CHP, PhD

Answer posted on 18 January 2002. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.