8. Magnesium

The name magnesium originates from the Greek word for a district in Thessaly called Magnesia. It is related to magnetite and manganese, which also originated from this area, and required differentiation as separate substances.

Magnesium is the fourth most common element in the Earth as a whole (behind iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet’s mantle. The relative abundance of magnesium is related to the fact that it is easily built up in supernova stars. Due to magnesium ion’s high solubility in water, it is the third most abundant element dissolved in seawater.

The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, it is coated in a thin layer of oxide, which partly masks this reactivity). The free metal burns with a characteristic brilliant white light, making it a useful ingredient in flares. The metal is now mainly obtained by electrolysis of magnesium salts obtained from brine. Commercially, the chief use for the metal is as an alloying agent to make aluminium-magnesium alloys, sometimes called “magnalium” or “magnelium”. Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.

The metal itself was first produced by Sir Humphry Davy in England in 1808 using electrolysis of a mixture of magnesia and mercuric oxide. Davy’s first suggestion for a name was magnium, but the name magnesium is now used.

In human biology, magnesium is the eleventh most abundant element by mass in the human body; its ions are essential to all living cells, where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNA. Magnesium ions are sour to the taste, and in low concentrations they help to impart a natural tartness to fresh mineral waters.

In vegetation magnesium is the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers.

Magnesium has a specific gravity of approximately 1.7; its alloys are the lightest of all engineering metals employed. The melting point of magnesium is 650° C; its boiling point is 1007° C. Magnesium is very inflammable and burns with a dazzlingflame, developing a great deal of heat.

Task 1. Match the terms with their definitions

1 solubility	the rate at which a chemical substance tends to undergo a chemical reaction
2 gravity	the quality, condition, or degree of being soluble or solvable
3 inflammable	produced by the union of several ingredients, parts, or things
4 compound	the force of attraction between all masses in the universe
5 reactivity	capable of being easily set fire; combustible

Task 2. Mark the sentences “True” or “False”

1) Magnesium is not found naturally on Earth, as it is highly reactive.

2)Magnesium is the fifth most common element in the Earth making up 13% of the planet's mass and a large fraction of the planet's mantle.

3) The mechanical properties of magnesium are very low and therefore pure magnesium is not employed in engineering.

4) The metal is now mainly obtained by electrolysis of a mixture of magnesia and mercuric oxide.

5) Magnesium ions are sweet to the taste.

Task 3. Match the beginnings of sentences to their endings

1 The relative abundance of magnesium is related to the fact that	using electrolysis of a mixture of magnesia and mercuric oxide.
2 Magnesium was first produced	to make aluminium-magnesium alloys.
3 The chief use for the metal is as an alloying agent	help to impart a natural tartness to fresh mineral waters.
4In low concentrations magnesium ions	with a dazzlingflame, developing a great deal of heat.
5 Magnesium is very inflammable and burns	it is easily built up in supernova stars.

Task 4. Complete the sentences with the appropriate words

a) alloying agent b) abundance c) electrolysis d) reactive e)solubility

Magnesium is the fourth most common element in the Earth as a whole. The relative _(1)_ of magnesium is related to the fact that it is easily built up in supernova stars. Due to magnesium ion’s high _(2)_ in water, it is the third most abundant element dissolved in seawater.

The free element is not found naturally on Earth, as it is highly _(3)_. The metal is now mainly obtained by _(4)_ of magnesium salts obtained from brine. The chief use for the metal is as an _(5)_ to make aluminium-magnesium alloys prized for their relative lightness and strength.