A Creation That Changed Science Forever: The Periodic Table

DmitrcropThere are several scientific developments and findings that have changed science for us today. These include the discovery of penicillin by Alexander Fleming and the discovery of the pasteurization process by Louis Pasteur, along with many more.  A scientific development that I find particularly interesting is that of the Periodic Table of Elements.

Russian chemist, Dmitri Mendeleev, made the first Periodic Table in 1869. As a young scientist, he wanted nothing more than to organise the subject. One day, Mendeleev spent his afternoon arranging cards, which had the symbols and atomic masses of various elements. Through doing this, he was able to spot patterns. After he had done this for several hours, he fell asleep at his desk. Mendeleev later wrote ‘In a dream I saw a table where all the elements fell into place as required, I immediately wrote it down on a piece of paper.’

Most scientists may often refer to Mendeleev when discussing the development of the Periodic Table because he officially wrote the elements down on paper. However, other scientists such as John Newlands, Henry Moseley, Lothar Meyer and Antoine Lavoisier contributed to its success. Mendeleev was the most popular amongst those mentioned because his devised table went beyond showing the organisation of elements; he proposed the existence of 8 new elements that were yet to be discovered.

As a chemist myself, I have grown to appreciate the importance of the Periodic Table, as I often refer to it to help me solve problems.  As once famously said by British chemistry research educator, Dennis Henry Rouvray, ‘Chemistry without the Periodic Table is as hard to imagine as sailing without a compass’. The numbers given on the table enable scientists to make calculations, which can be very helpful in industrial processes. Elements with similar properties are grouped together; therefore, predictions about the reactivity of a selected element can be made solely based on its position on the table.  Mendeleev originally created a table that consisted of 8 columns and 12 rows.  He realised that the chemical properties of elements were related to their atomic mass. This enabled him to arrange elements with similar atomic numbers in the same vertical columns.  Mendeleev left gaps in his original table, as he thought that some elements were yet to be discovered.  He cleverly worked out the atomic numbers of these mystery elements, hence noting their position on the table. Other scientists later discovered these elements; Mendeleev’s calculations turned out to be correct.  For example, he rightly placed an undiscovered element under aluminium on the Periodic Table; this element, gallium, was discovered six years later in 1875, and its chemical and physical properties matched Mendeleev’s predictions.

Science is constantly changing and evolving. The appearance of the chart has changed. Initially, Mendeleev’s table contained 63 elements.  However, modern day Periodic Tables contain 118 elements.  Modern day scientists have retained Mendeleev’s use of columns and rows. The rows of today’s tables show elements in order of Mendeleev’s columns.  Elements found in the same column (group) of the Periodic Table have the same number of electrons on their outermost shell and therefore they have similar chemical properties. For example, elements such as lithium and potassium have 1 electron on their outer shell and they both react with water to produce a metal hydroxide and hydrogen gas. Elements in the same row (period) have the same number of orbitals.  As you move down the periods, each row adds an extra orbital. Another alteration that was made to the table came later in 1913; British chemist, Henry Moseley, thought it best to organise the elements in order of increasing atomic number, rather than atomic mass. The Periodic Table is logical, which shows Mendeleev achieved his goal of carefully arranging his chemical knowledge.

Mendeleev’s work has undoubtedly revolutionised chemistry. His achievements were crowned with the Copley Medal in 1905. The British Royal Society gave him this prize for his innovative discovery, the Periodic Table. The Periodic Table shows us the vast range of substances that exist: around 98 elements exist naturally while others have only been made in nuclear reactors.  Substances are always being reviewed and analysed, as they could potentially be new elements.  As someone who is deeply passionate about chemistry, my understanding of elements and the subject as a whole is strongly supported by this development.

To find out more, please click on the following link https://www.youtube.com/watch?v=0RRVV4Diomg .

Farida (LVI)