The metals

It is now 2,000 years since Julius Caesar was stabbed in a small auditorium known as Pompey’s Curia and his body cremated in the Roman Forum. Since that time, many changes have taken place. Yet, in a sense, many things have remained the same. Steel is still the basic material of armaments, although, to be sure, it is not used in the manufacture of shields and short swords. Gold, silver, and copper are, as 2,000 years ago, the Erin coinage metals. Bronze is still used for objects intended to resist the corrosive action of the atmosphere, but now it has many competitors.

Knowledge of the metals, of course, has increased, greatly since Caesar’s day. Yet, the average citizen might have difficulty in naming more than twice as many metals as a Roman could. The Roman world knew, at least, copper, lead, gold, silver, tin, dion, mercury, and zinc (in a copper alloy). To this list, the twentieth-century's man in the street might add aluminum, magnesium, nickel, chromium, cobalt, tungsten, molybdenum, uranium, and one or two others. If he happened to be interested in aeronautics, he might add titanium. Almost certainly, he would be unable to name more than a third of the known metals.

Questions now arise as to how metals may be distinguished from non-metals and how many metals are known. Both iron and oxygen are chemical elements but only the first is a metal. One asks, “On what basis is this distinction made?” On a chemical basis, little distinction can be made. Both metals and non-metals enter actively into chemical reactions. The difference reveals itself in the physical properties. By common agreement, those elements that possess high electrical conductivity and a lustrous appearance in the solid state are considered to be metals.

2. Find in the text English equivalents to the following words and word combinations:

захищати від корозії, зброя, мідь, свинець, олово, ртуть, вольфрам, молібден, уран, взаємодіяти у хімічних реакціях, електропровідність, блискучий зовнішній вигляд.

3. Translate the following groups of words:

conduct – conductive – conductivity; luster – lustrous; appear – appearance.

Дата добавления: 2015-07-25