Editorial Feature

How Has the Periodic Table Changed in the Past 20 Years?

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The periodic table is a chart that organizes the arrangement of the known and recognized chemical elements. The organization on the table is based on the atomic weight, electron configurations, and chemical properties of the elements. The elements are shown according to their increasing atomic weights, starting with the smallest and gradually moving up to the highest weights.

Most people have been seeing the periodic table on classroom walls since grade school, and most people probably think it never changes. They're wrong. The periodic table is much more fluid than the majority of people realize. It's still changing today.

The first periodic table in the "rows and columns" form we see today was invented by Dmitri Mendeleev in 1869. It included the properties of all of the known elements of that time. Mendeleev predicted that the discovery of some as-yet unknown elements would fill in some of the gaps on his table at some point in the future, and he was correct.

The periodic table has long-since filled in Mendeleev's gaps and has added new elements. It has even changed the weights of other elements. The periodic table is continually being changed as new discoveries are made and new theories are developed to explain the behavior of chemicals.

A huge number of changes were made to the periodic table in the early parts of the 20th century. However, some interesting and significant changes have been made as recently as the past 20 years. For example, two brand new elements were discovered in 2004 and 2006 respectively, and added to the periodic table in 2012. These elements are flerovium (element 114) and livermorium (element 116).


Mendeleev's periodic table was the first in rows and columns.Image Credits: Atomic Structure

Flerovium and livermorium are short-lived elements, each lasting only seconds or less. They are lab-created elements that scientists made as side effects of smashing the atoms of other elements together to see what they would do. These aren't elements you'll likely find out in nature, but they are elements nonetheless and now have proud places on the periodic table.

These two new elements now make the number of elements displayed on the periodic table 117. However, only 114 of these elements are officially recognized by the scientific community. Elements 113, 115, and 117 have not yet been officially accepted as genuine elements.

The number of elements on the periodic table isn't the only thing about the table to change in the past 20 years. The atomic weights of some elements on the table have also been changed. These changes were made by the International Union of Pure and Applied Chemistry (IUPAC), which is the organization that oversees the official periodic table.

IUPAC decided that the atomic weights of the elements bromine and magnesium varied from atom to atom more than was previously realized.

This made their weights better expressed as intervals of numbers rather than as single numbers. Bromine used to have an atomic weight of 79.904 on the periodic table. It now has an interval of 79.901 to 79.907. As for magnesium, it once had an atomic weight of 24.3050. Now, the periodic table shows it as 24.304 to 24.307. The elements germanium, indium, and mercury are also expected to get official atomic weight changes on the periodic table in the near future.

As new discoveries continue to be made, the periodic table will continue to change. It is almost like a living document in that it grows and expands as new information is fed to it. The periodic table of 20 years ago is gone. The periodic table of 20 years from now is still waiting to be discovered.

Kris Walker

Written by

Kris Walker




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  1. Karl Erik Aune Karl Erik Aune United States says:

    My textbook "Organic Chemistry" Fessenden, 1990, lists Lawrencium (element 103) as Lw. Current periodic tables show Lr. I cannot guess at the cause of the discrepancy.

    Similarly, element 104 is represented by Ku in my textbook. That is odd, because I believe it was recognized as Rutherfordium (Rf) back then. Perhaps there was a naming issue as the following.

    In 1970, element 105 was discovered at Berkeley, and allegedly also in Dubna, Russia. The Berkeley team was unable to reproduce the Soviet discovery with better equipment. The Berkeley team used the name Hahnium, but IUPAC recommended the name Dubnium in 1977. Hahnium was already in common parlance, and element 105 is labelled Ha in my 1990 textbook. Today 105 is Db.

    Thus I suggest that many more changes have been made to the periodic table than you suggest. Even if some changes are more localized than others.

    • D C D C United States says:

      I’ve been trying to find a 1990 table. Is 74 W listed as Wolfram or Tungsten?


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