MT. Types of Elements

MT. Types of elements

[Properly not a subset of ‘elements’ but rather a set of supersets of individual elements. If we had used the ME class indicator we would have risked confusion with isotopes of particular elements.]

1. Alkali Metals (Lithium, Sodium, Potassium, Rubidium, Cesium, Francium)

2. Alkaline Earth Metals (Beryllium, Magnesium, Calcium, Strontium, Barium, Radium)

3. Transition Metals (38 of them)

4. Other Metals (Aluminum, Gallium, Indium, Tin, Thallium, Lead, Bismuth)

5. Metalloids (Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Polonium)

6. Non-Metal elements (Hydrogen, Carbon, Nitrogen, Oxygen, Phosphorus, Sulfur, Selenium)

7. Halogens (Fluorine, Chlorine, Bromine, Iodine, Astatine)

8. Noble gases (Helium, Neon, Argon, Krypton, Xenon, Radon)

9. Rare earth elements (15 each in the Lanthanide (9l) and Actinide (9a) series)

M. Metals (the five metal classes)

Note: Astatine is sometimes termed a metalloid.

[We do not review at length here the justifications for these groupings, which reflect understandings of the common nature of these groups – and thus of their common uses. It is of course possible that other groupings and sub-groupings would be valuable for other purposes. These can be represented by MT0. ]

Birger Hjorland (in Journal of Documentation 68:3) has noted that helium may be both a noble gas and rare earth.

One possible way of grouping elements is in terms of electron orbit.

The periodic table of elements can also for some purposes usefully be divided into columns [See MG. Groups of Elements] or rows [See MP. Periods of Elements].