July 30, 2012
Elizabeth Frayne, PhD.
Atoms, Molecules, and Elements
Dmitri Ivanovich Mendeleev (1834-1907) was a Russian chemist famous for his formulation of classification of elements, or what is now called the Periodic Table of Elements (2011). On 6 March 1869, Mendeleev made a formal presentation to the Russian Chemical Society, titled “The Dependence between the Properties of the Atomic Weights of the Elements”, which described elements according to both atomic weight and valence. This presentation stated that: the elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties; elements which are similar in regards to their chemical properties have atomic weights which are either of nearly the same value (e.g., Pt, Ir, Os) or which increase regularly (e.g., K, Rb, Cs); the arrangement of the elements in groups of elements in the order of their atomic weights corresponds to their so-called valence’s, as well as, to some extent, their distinctive chemical properties; as is apparent among other series in that of Li, Be, B, C, N, O, and F; the elements which are the most widely diffused have small atomic weights; and that the magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body (2011).
It is essential to consider the electronic structure of atoms when looking at the Periodic Table of Elements. According to Rockley, El-Ashmawy, and Burke (2010), “Elements that exhibit similar properties were placed together in the same column of the table. When atoms react, it is the electrons that are interacting. The arrangement of electrons in an atom is called its electronic structure” (Chapter 6 para.2). The electronic structure of an atom refers not only to the number of electrons that an atom possesses but also to their distribution around the nucleus, as well as their...