An online version of one of the most useful tools for students for understanding chemistry and the chemical elements that make up the world around us was  featured recently by  the Voice of America (VOA) as  its ‘Website of the Week’. 

The website – www.periodic.lanl.gov – is  hosted by Los Alamos National Laboratory in New Mexico, and gives much useful information on ‘The Periodic Table of the Elements’.  Originally designed as an internal resource for the laboratory, it has evolved into a general reference source, mainly focused on chemistry students in the mid- and high-school age groups. 

The site has an easy-to-use format and a feedback channel for questions and comments.

The periodic table of the elements  has been around, in one form or another, since the mid-19th century.  Russian chemist Dmitri Mendeleev is generally credited with devising the first version in 1869, but it has been modified over the years, first on paper and now online in various versions, including the one hosted by  Los Alamos.

The periodic table is an ordered table of all the elements arranged by their atomic numbers, i.e., the number of protons and electrons in an atom.

The arrangement means that elements with similar properties are grouped near to each other. 

The horizontal rows are called ‘periods’, and the vertical rows are ‘groups’.  Elements with the same number of electrons in their outer shell behave in a similar way, and this is the basis of  the vertical group.  Moving from left to right along the periods corresponds to the gradual filling of successive electron shells and an increase in the size of the atom.

Mendeleev’s first periodic table was based upon atomic weights.  This basic principle, subsequently modified to use atomic numbers rather than atomic weights, formed the basis of the modern table.

Like any periodic table, the online version features the chemical symbol, atomic weight, and atomic number for each of  the known elements.  It also offers in-depth information about each element, such as the history related to its discovery, various properties, uses and costs of  the element.

For added value, the Los Alamos Laboratory has also included information on how to use the periodic table, how elements get their names, and more.

The website was named by ScientificAmerican.com (part of  Scientific American magazine) in May 2001 as one of the top 50 web resources in science and technology.

“The Web offers any number of  periodic charts, but this one from  Los Alamos National Laboratory is by far among the best,” according to the magazine.