foretold their main properties by considering the properties of contiguous elements, which were already known. A few years later three elements were discovered having almost exactly the properties foretold by Mendeleyev. These elements were: gallium, germanium and scandium.

II. Проанализируйте и письменно переведите следующие предложения. 1.Nitrogen is known to be an essential element in most of the substances which

make up living matter.

2.Oxygen combining with another substance, an oxide is formed.

3.Were helium obtained only from the air, it would be considered a rare gas. 4.While working at his table Mendeleyev could predict the existence of some

unknown elements.

ВАРИАНT 2

I. Перепишите и переведите текст письменно.

COPPER

Copper is found native and some of its ores are easily reduced, copper and bronze have therefore been used from very early times. The Romans obtained copper from Cyprus; they called it as cyprium and subsequently cuprum; hence the symbol Cu.

Copper ores are widely distributed throughout the world.

Copper, when newly mined and deposited in electrolysis or freshly reduced from the oxide, is salmon pink in colour, but the metal soon tarnishes, the light transmitted through copper leaf is green. Most cupric compounds are blue or green, the solutions are also blue or green.

The metal melts at 1084°C and boils at 2336 °C. It is malleable and ductile, and can therefore be hammered out into thin sheets, or drawn into wire. Just below the melting-point, however, it becomes brittle. It is a very good conductor of heat and electricity (second only to silver) and is widely used on this account.

Copper is stable in dry air, but if it is exposed in moist air for a long time, it becomes covered with a green coating; this is a basic sulphate. This green patina is formed slowly. In places by the sea-shore, the coating is essentially a basic chloride.

On heating in dry air, Copper becomes covered with a black film of cupric oxide (CuO) and if this film is scratched, a red film of cuprous oxide, Cu2O, is found under the black.

The metal is without action on water and at a white heat is only slightly attacked steam.

If copper is heated with concentrated sulphuric acid it dissolves and sulphur dioxide is liberated. The oxidizing agent here is the sulphuric acid.

The equation is sometimes represented as Cu + 2H2SO4 = CuSO4 + 2H2O+ SO2

but cuprous sulphide, Cu2S, and cupric sulphide, CuS, are also formed. Copper does not react with alkalis.

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