Preparation

Beryllium is obtained by two most important methods:

1. Reduction of BeF₂ with metallic magnesium

BeF₂ + Mg = MgF₂ + Be (powder)

2. Electrolysis of molten mixture BeCl₂ + NaCl (at 350С) at cathode: Be²⁺ + 2e = Be

Magnesium is obtained by:

1. Electrolysis of fused MgCl₂ or carnalitte. Obtaining 1 ton of Mg requires about 20 MWt-hours of electric energy.

2. Electrothermal method is based on the reversible reaction:

MgO + C Mg + CO H = 640 kJ/mol,

equilibrium of which is displaced to the right at higher than 2000C temperature. MgO mixture with grinded coal is made red hot in electric furnace, the vapor of Mg which is formed, is mixed up with strongly cooled gaseous Н₂ at the exit of the furnace. The temperature there quickly drops to 150-200C so that there is no time for equilibrium to be desplaced to the left. Dust-like magnesium obtained is then remelted.

In industry:

Ca and Sr: 1. Electrolysis of molten mixtures CaCl₂ and CaF₂; SrCl₂ and KCl,

2. Alumothermy in vacuum:

4CaO + 2Al = 3Ca + CaO·Al₂O₃

2SrO + 2Al = 3Sr + Al₂O₃

Ba: alumino- or silicothermy in vacuum at  1200С:

3BaO + 2Al = 3Ba + Al₂O₃

3BaO + Si = 2Ba + BaSiO₃

The annual production of metallic Са makes up several thousand tons, the output of Sr and Ba is much less because of much less application. The Ra accumulated world wide makes up about 2.5 kg.

Uses

Magnesium is the third most commonly used constructional metal, following steel and aluminium. In large volumes Mg is used in a free state: reducing agent in metallothermy, corrosion protection (marine ships, gas pipelines), for making of strong and light alloys (mostly in automotive and truck components – alloy of Mg with Al (magnaly) and under the name “electron” a series of Mg alloys with Al (up to 10.5%), Zn (up to 4.5%) and Mn (up to 1.7%) is known. An interesting feature of these alloys is that they (unlike Al), are indifferent towards solutions of alkalis and HF. Economy of mass which is achieved as a result of using the electron, makes up nearly 80% as compared to Fe, 20-40% - with duralumin, more than 40% - with wood.

Metallic Be is used for making “windows” in X-ray devices (radiation windows for X-ray tubes). Beryllium, due to its low atomic number, is highly transparent to X-rays. Its alloys with copper (up to 2% Be only) are named beryllium brasses. They have steel hardness and extraordinarily high mechanical strength. Remember that Be is poisonous.

Alkaline-earth metals chemical properties (1)

Ca, Sr, Ba. These metals are very reactive. Activity grows towards Ва.

Already in the dry air Ca, Sr, Ba surfaces are quickly covered with gray films, which are not protective and consist of oxide, peroxides and nitrides.

2Ca + O₂ = 2CaO

Ba + O₂ = BaO₂

3Sr + N₂ Sr₃N₂

In moist air they gradually form hydroxides and carbonates, therefore these metals behave similarly to alkali metals.

At STP they react with non-metals very vigorously. At slight heating they also react with usually chemically extremely inert N₂. Akaline-earth metals interact with C, Si, B at high temperatures:

Me + 2C MeC₂

Me + 2Si MeSi₂

Me + 6B MeB₆

Except for halogenides and chemically stable refractory borides, those binary compounds are decomposed even in water with the formation of hydroxides and hydrogen compounds:

Me₃N₂ + 6H₂O = 3Me(OH)₂ + 2NH₃

MeC₂ + H₂O = Me(OH)₂ + C₂H₂

At elevated temperatures Ca, Sr, Ba react with Н₂ with the formation of stable hydrides МeН₂.

Their reaction with water and acids results in the formation of H₂, and with HNO₃ they form NH₄NO₃.

At heating alkali-earth reduce metals and non-metals oxides to the elemental substances, which is used (especially, Ca) for obtaining of free metals (U, Th, Cr, V):

V₂O₅ + 5Ca 5CaO + 2V