WebElements

Periodic Table

strontium

Atomic number: 38
Atomic weight: 87.62
Symbol: Sr
Group number: 2
Electronic configuration: [Kr].5s2

Description

Strontium does not occur as the free element. Strontium is softer than calcium and decomposes water more vigorously. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish colour with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart an excellent crimson colour to flames, and these salts are used in pyrotechnics.

Strontium-90 (90Sr) has a half-life of 28 years. It is a product of nuclear fallout and presents a major health problem. Strontium titanate is an interesting optical material as it has an extremely high refractive index and an optical dispersion greater than that of diamond. It has been used as a gemstone, but it is very soft.

General information

Discoveror: Adair Crawford
Date discovered: 1790
Discovered at: Scotland
Meaning of name: Named after the village of "Strontian" in Scotland

Physical data

Standard state: solid at 298 K
Colour: silvery white
Density of solid at ambient temperature/kg m-3: 2630
Molar volume/cm3: 33.94

Radii /pm

Atomic: 219
Covalent (single bond):
Pauling radius for the ion [Sr]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius204.5no datano datano data

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 0.95
Allred Rochow: 0.97

Crystal Structure

structure: ccp (cubic close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

ball-and-stick.gif

Temperatures (/K)

melting point: 1050
boiling point: 1655

Enthalpies /kJ mol-1

fusion: 7.4
vaporization: 136.9

single bond enthalpies:
Sr-F Sr-Cl Sr-Br Sr-I Sr-Sr
553 469 405 335 15.5

Ionization enthalpies /kJ mol-1

Number Enthalpy
1st549.5
2nd1064.2
3rd4210
4th5500
5th6910
6th8760
7th10200
8th11800

Isotopes

This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
84Sr83.913430 (4)0.56 (1)
86Sr85.9092672 (28)9.86 (1)
87Sr86.9088841 (28)7.00 (1)
88Sr87.9056188 (28)82.58 (1)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Sr.html