ME. Chemical Elements

ME The Chemical Elements.

The chemical elements represent individual atoms, with different elements being determined by the number of protons that they possess.

ME represents elements in general (whereas atoms are WC2) [See WC. Composite Particles]

Each element has been given by the chemistry profession a one or two digit letter symbol and a 1-3 digit number representing the number of protons. Since the symbols are more recognizable and slightly more compact we will use them here. Thus: MEK is Potassium, MEH is hydrogen, and MEHe is Helium.

It is sometimes useful to note whether an element (or molecule, below) carries a positive or negative charge. Common practice in chemistry is to indicate a positive or negative charge of 1 by the use of + or – after the symbol, and greater charges by the use of the numbers 2 and up after the + or -. To avoid confusion with other uses of + or – in this classification we will instead just use numbers to denote positive charge and underlined numbers to denote negative charge. Thus:

· MENa1 is Sodium with a positive charge of 1

· MEO2 is oxygen with a negative charge of 2.

Note: Elements carrying a charge are referred to as ions. It is often maintained that the word atom should be limited to elements with no charge. But ions are treated here as a subset of the word atom. Note that the existence and size of electrical charge represents exactly the difference in numbers of protons and electrons within the ‘atom.’ Treating ions as a subset of ‘atoms,’ and thus treating atoms with different numbers of electrons as subsets of an element associated with a particular number of protons, parallels the common treatment of isotopes (which reflect differences in the number of neutrons) as subsets (see below).

Though elements are defined in terms of the number of protons, a particular element may contain different numbers of neutrons. These different types of a particular element are referred to as isotopes. The common practice in chemistry is to designate isotopes by references to their atomic mass rather than the number of neutrons, and to provide this number before the symbol. We can follow that practice here. Thus:

· ME238U represents the most common isotope of Uranium

· ME127I1 represents an Iodine atom isotope 127 with negative charge 1.

Note that following common practice of placing mass before symbol allows us to indicate both isotope and charge without confusion.

General references to isotopes or electrical charges can be captured by use of:

ME(2) for isotopes

ME(QN7) for electrically charged elements

These should in turn be linked to particular isotopes and charges.

Scholars of science studies have long noted that chemists might have chosen to classify chemical elements differently. Rather than privileging the number of protons, and treating the number of electrons and neutrons secondarily, they might instead have privileged neutrons, electrons, atomic mass, or some other characteristic. Two points can be made: First it seems that the number of protons is of greatest importance: we will see below that it makes sense to organize elements defined in terms of number of protons into groups of similar elements. Second this empirical fact reflects widely held theoretical understandings (which could of course change) of how atoms work and thus why different elements behave differently.