Strontium

Strontium,  ₃₈Sr

General properties
Name, symbol	Strontium, Sr
Appearance	Silvery-white
Strontium in the periodic table
Ca ↑ Sr ↓ Ba Rubidium ← Strontium → Yttrium
Atomic number	38
Standard atomic weight (Ar)	87.62(1)
Group, block	(alkaline earth metals); s-block
Period	period 5
Electron configuration	[Kr] 5s2
per shell	2, 8, 18, 8, 2
Physical properties
Silvery-white
Phase	Solid
Melting point	1050 K ​(777 °C, ​​1431 °F)
Boiling point	1650 K ​(1377 °C, ​2511 °F)
Density near r.t.	2.64 g/cm3
when liquid, at	2.375 g/cm3
Heat of fusion	7.43 kJ/mol
Heat of	141 kJ/mol
Molar heat capacity	26.4 J/(mol·K)
pressure
Atomic properties
Oxidation states	2, 1 ​(a strongly basic oxide)
Electronegativity	Pauling scale: 0.95
energies	1st: 549.5 kJ/mol 2nd: 1064.2 kJ/mol 3rd: 4138 kJ/mol
Atomic radius	empirical: 215 pm
Covalent radius	195±10 pm
Van der Waals radius	249 pm
Miscellanea
Crystal structure	​
Thermal expansion	22.5 µm/(m·K) (at 25 °C)
Thermal conductivity	35.4 W/(m·K)
Electrical resistivity	132·10-9 Ω·m (at 20 °C)
Magnetic ordering	Paramagnetic
Young's modulus	15.7 GPa
Shear modulus	6.03 GPa
Poisson ratio	0.28
Mohs hardness	1.5
CAS Registry Number	7440-24-6
History
Naming	After the mineral strontianite, itself named after Strontian, Scotland
Discovery	William Cruickshank (1787)
First isolation	Humphry Davy (1808)

Strontium is an alkaline earth metal with the symbol Sr and atomic number 39.

Properties

Chemical

Strontium metal bubbles fiercely on contact with water. It burns in air to produce both strontium oxide and strontium nitride, but since it only reacts with nitrogen above 380 °C, at room temperature it will only form the oxide.

The chemistry of strontium salts is similar to barium (nigh insoluble sulfate and carbonate, soluble chloride and nitrate), so strontium salts can be used as a safer, non-toxic alternatives to barium salts when detecting sulfate ions.

Physical

Strontium metal is soft and silvery. Its salts tend to produce a scarlet-red flame when burned in a flame.

Availability

Strontium metal may be purchased at GalliumSource, at 85$/ 2.5 kg.

You can also buy celestine, a mineral of strontium consisting mainly of its sulfate, from mineral collector stores. Finely ground celestine can be subjected to the Curie reaction (lengthy boiling under reflux with sodium carbonate) to convert it to strontium carbonate, which is a useful precursor to any strontium salt.

Additionally, most red-colored road flares contain strontium in the form of the nitrate, along with elemental sulfur and a binder. This can be crystallized out of the solution for a decent yield of pure, snow-white strontium nitrate.

Preparation

Strontium is difficult to prepare and cheap to buy, so it is worth just buying the metal.

Projects

• Colored flames
• Make strontium titanate
• Make strontium salts

Handling

Safety

Strontium salts are non-toxic. They have been investigated for positive effects on bone mass, and strontium supplements are beginning to hit the market. However, that does not imply that consuming strontium salts produced in the lab is safe.

Storage

Just like calcium and all the alkali-earth metals under it, strontium metal corrodes easily on contact with air and water and must be stored under oil or in an inert atmosphere. The metal presents a fire hazard. Class D fire extinguishers should be used with strontium fires. Water will cause a hydrogen explosion.

Disposal

Strontium can be safely disposed by reacting it with water or isopropanol and doesn't pose a hazard to the environment, so no special disposal is required.

References

Relevant Sciencemadness threads

• Metallic Strontium
• casting strontium metal dendritic form?
• Strontium and Barium