Quantitative Description
| Element |
|
|
Band structure | ||
| Boron | 191 | 2.04 | semiconductor | ||
| Silicon | 187 | 1.90 | same | ||
| Germanium | 182 | 2.01 | same | ||
| Arsenic | 225 | 2.18 | semimetal | ||
| Antimony | 198 | 2.05 | same | ||
| Tellurium | 207 | 2.10 | semiconductor | ||
| average | 198 | 2.05 | |||
| The elements commonly recognized as metalloids, and their ionization energies (kcal/mol); electronegativities (revised Pauling scale); and electronic band structures (most thermodynamically stable forms under ambient conditions). | |||||
Metalloids tend to be collectively characterized in terms of generalities or a few broadly indicative physical or chemical properties. A single quantitative criterion is also occasionally mentioned.
Masterton and Slowinski give a more specific treatment. They wrote that metalloids have ionization energies clustering around 200 kcal/mol, and electronegativity values close to 2.0. They also said that metalloids are typically semiconductors, 'although antimony and arsenic have electrical conductivities which approach those of metals'. Their description, using these three more or less clearly defined properties, encompasses the six elements commonly recognized as metalloids (see table, right). Selenium and polonium are probably excluded from this scheme; astatine may or may not be included.
In other quantitative terms, the elements commonly recognized as metalloids have:
- Packing efficiencies of between 34% to 41%. That of boron is 38%; silicon and germanium 34; arsenic 38.5; antimony 41; and tellurium 36.4. These values are lower than the values of most metals (at least 80% of which have a packing efficiency of at least 68%) but higher than those of elements usually classified as nonmetals. Packing efficiencies for nonmetals are: graphite 17%, sulphur 19.2, iodine 23.9, selenium 24.2, and black phosphorus 28.5.
- Goldhammer-Herzfeld criterion ratios of between ~0.85 to 1.1 (average 1.0).
Read more about this topic: Metalloid
Famous quotes containing the word description:
“The next Augustan age will dawn on the other side of the Atlantic. There will, perhaps, be a Thucydides at Boston, a Xenophon at New York, and, in time, a Virgil at Mexico, and a Newton at Peru. At last, some curious traveller from Lima will visit England and give a description of the ruins of St Paul’s, like the editions of Balbec and Palmyra.”
—Horace Walpole (1717–1797)