by Jamie Craig

Created on: December 04, 2009

Understanding Atomic Structure

Atomic structure is actually remarkably simple to understand; despite the fact a definite atomic structure hadn't being cemented until the early 19th century. There are three main components to the atom: electrons, neutrons and protons. All three are summarised below.

>>Protons<<

Protons are positively charged sub-atomic particles which have a relative atomic weight of 1 and a charge of +1. They exist in the centre of the atom in the "nucleus". The entire nucleus is held together by nuclear forces (sometimes called "residual strong force") and contains within it 99.9% of the atom's mass concentrated into one tiny spot.

>>Electrons<<

Electrons have a miniscule relative atomic mass (approximately 1/1836th of a neutron) however they do have a negative charge of -1. This means that they effectively "cancel out" the positive charges of the protons when examining the atom as a whole, however contribute nothing to the overall mass. Electrons are organised into shells/orbits around the the central nucleus in what is commonly compared to planets orbiting a star. The positions of these electrons are maintained by electromagnetic forces created due to the differentce between the charges of protons and electrons. Whilst the "reality" of electrons is that they exist in a quantum "cloud" around the nucleus the more conventional way of thinking allows us to make extremely accurate predictions about how an atom will react with other elements and the characteristics the element will have.

Whilst electronic configuration is a complex enough subject to be addressed in an entirely different article (or indeed a series of articles) it can simplified into some commonly used notations that are effective for common chemical applications. The electron configuration for Argon is shown below, the latter of which takes into account sub-orbitals.

- Electron per Shell: 2, 8, 8

- Electron Configuration: 1s2, 2s2, 2p6, 3s2, 3p6

>Key for Electron Configuration:

+ 1st Number- the shell number

+ 1st Letter- the type/location of the sub-orbital into which shells are divided named "blocks".

+ 2nd Number- the number of electrons found in this sub-orbital.

[It should be noted that Argon is one of the last elements before the transition metals in which electronic configuration becomes more complicated by the inclusion of "d-blocks" and thus has been left out of this article.]

In very general terms atoms with 1 or 2 electrons in their outer

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