Back to basics

An Overview of Water Chemistry

By Lee Comb


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Welcome to our archive. This article by Lee Comb was published in December 2008. It examines the fundamental aspects of water chemistry in a way that provides useful background for technicians who work with water, and others wanting to learn more about this subject. It is part of our “Back to Basics” series.

“What’s an atom?”, asked a woman in the back row of a presentation on water chemistry many years ago, just as the speaker was moving into a description of the reasonably advanced topic of oxidation states.  It was very apparent there was a need to “go back to the basics”.  Speaking on behalf of many who have dealt with water and water chemistry for many, many years, perhaps all of us could learn something by going back-to-the-basics. 

Atomic Building Blocks

An atom represents the basic building blocks of the universe as we know it.  While composed of sub-atomic particles (e.g., electrons, neutrons, protons, and others), the atom could be equated to the bricks that build the building and the sub-particles are the sand, water and clay that make up the brick.  Our focus is how the various bricks – or atoms – affect our water chemistry.

The different atoms are composed of a nucleus containing a representative number of protons (positively charged sub-atomic particles) and often neutrons (neutral sub-atomic particles).  Orbiting around the nucleus are electrons (negatively charged sub-atomic particles) – in normal circumstances – of a quantity equal to the number of protons.  Atoms with an imbalance of electrons versus protons are called “ions” and atoms – of the same species, but containing different numbers of neutrons – are called “isotopes”.

The whole set of atoms is graphically presented in the Periodic Table, created by Mendeleef in the late 19th century.  Mendeleef had noted that the various atoms could be grouped according to similar physical properties and he placed them in columns of similar behaving elements.  The periodic table offers a wealth of information, including atomic weights, oxidation states, electro-negativity, among a host of other facts, many of which play an important role in understanding water and the related chemistry. 

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