Group 2 / IIA; Alkaline Earth Metals Group

Calcium (Ca) and magnsium (Mg) are ubiquitous; the rest is rarer; Radium is radioactive and thus only found in radioactive decay chains. Alltogether the earth alkali metals account for abount 4 % of the crust of the earth. Like the alkali metals they are very reactive and thus never found in the elemental state.
All are silvery-shining metals that oxidize immdiately in air. Stable oxide layers, however, protect some of beryllium (Be) and magnesium (Mg) so they can be used in their metallic state and are stable in water (which dissolves the others)
Magnesium (Mg), calcium (Ca) are technically important (not to mention the biological importance of calcium). The rest also finds special uses.
Table of Basic Data
 
Name
(German)		 Beryllium
Beryllium 		Magnesium
Magnesium 		Calcium
Calcium 		Strontium Strontium Barium
Barium 		Radium
Radium
Atomic number 4 12 20 38 56 88
Atomic mass [u] 9,01 24,31 40,08 87,62 137,33 226,03
Melting point [K] 1551 921,95 1112 1042 998 973
Melting point [oC] 1278 648,95 839 769 725 700
Melting point [oF] 2332 1200 1542 1416 1337 1292
Boiling point [K] 3243 1380 1760 1657 1913 1413
Density [g/cm3] 1,85 1,74 1,54 2,63 3,65 5,50
Ionization energy [eV] 9,32 7,65 6,11 5,70 5,21 5,28
Electro-negativitiy 1,5 1,2 1,0 1,0 1,0 1,0
Atomic radius [pm] 113,3 160 197,3 215,1 217,3 223
Ionic radius [pm] 34 78 106 127 143 152
Oxidation numbers 2 2 2 2 2 2
lattice typ
Transformation temp. [oC]		 hcp hex hcp
440
fcc		 bcc
540
hcp
234
fcc		 bcc ?
Lattice constant [Å]
(a or c)		 2,29 3,20 5,56
?		 6,09
?		 5,02 ?
Young's - Modul us [GPa] 310 44,3 19,6 15,7 12,7 ?
Therm. expansion coefficient a
[10-6K-1]		 11,5 26 22 ? 19 ?
 
In case of doubt all numbers are for room temperatures
fcc = face centered cubic; lattice const. = a
bcc = body centered cubic
sc = simple cubic
hp = simple hexagonal
hcp = hexagonal close packed; lattice constants a and c.
op = simple orthorhombic, monoclinic, triclinic
tp = simple tetragonal
dia = diamond structure
r = trigonal or rhomboedral trigonal

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© H. Föll (Iron, Steel and Swords script)