Strontium: reactions of elements
Reaction of strontium with air
Strontium is a silvery white metal. The surface of strontium metal is covered with a thin layer of oxide that helps protect the metal from attack by air, but to a lesser extent than the corresponding layer in magnesium. Once ignited, strontium metal burns in air to give a mixture of white strontium oxide, SrO, and strontium nitride, Sr3N2. Strontium oxide is more normally made by heating strontium carbonate. Strontium, two places below magnesium in the periodic table is more reactive with air than magnesium.
2Sr(s) + O2(g) → 2SrO(s)
3Sr(s) + N2(g) → Sr3N2(s)
Reaction of strontium with water
Strontium reacts slowly with water. to form strontium hydroxide, Sr(OH)2 and hydrogen gas (H2). The strontium metal sinks in water and after a short while bubbles of hydrogen are evident, stuck to the surface of the metal. The reaction is quicker than that of calcium (immediately above strontium in the periodic table) but slower than that of barium (immediately below strontium in the periodic table).
Sr(s) + 2H2O(g) → Sr(OH)2(aq) + H2(g)
Reaction of strontium with the halogens
Strontium is very reactive towards the halogens chlorine, Cl2 bromine, Br2, or iodine, I2, and burns to form the dihalides strontium(II) chloride, SrCl2, strontium(II) bromide, SrBr2, and strontium(II) iodide, SrI2 respectively. The reaction with bromine takes place at about 400°C and that with iodine at a dull red heat.
Sr(s) + Cl2(g) → SrCl2(s)
Sr(s) + Br2(g) → SrBr2(s)
Sr(s) + I2(g) → SrI2(s)
Reaction of strontium with acids
Strontium metal dissolves readily in dilute or concentrated hydrochloric acid to form solutions containing the aquated Sr(II) ion together with hydrogen gas, H2.
Sr(s) + 2HCl(aq) → Sr2+(aq) + 2Cl-(aq) + H2(g)