Light metals

from Wikipedia, the free encyclopedia
The elements, sorted according to metal properties and density.
Non-metals: up to 5 g / cm³
(semi-) metals (light metals): up to 5 g / cm³ from 5 g / cm³ from 10 g / cm³ from 20 g / cm³
H Hey
Li Be B. C. N O F. No
N / A Mg Al Si P S. Cl Ar
K Approx Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mon Tc Ru Rh Pd Ag CD In Sn Sb Te I. Xe
Cs Ba La * Hf Ta W. re Os Ir Pt Au Ed Tl Pb Bi Po At Marg
Fr. Ra Ac ** Rf Db Sg Bra Hs Mt Ds Rg Cn
 
  * Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho He Tm Yb Lu
  ** Th Pa U Np Pooh At the Cm Bk Cf It Fm Md No Lr

Metals and alloys with a density below 5.0 g / cm³ are generally referred to as light metals . All other metals are heavy metals , of which europium is the lightest with a density of 5.244 g / cm³. In the technical field, aluminum, magnesium, titanium and, to a lesser extent, beryllium and lithium are used - as well as other elements as alloying elements in low concentrations. The processing of metallic materials with light metals is basically the same as with other metals.

List of light metals

A complete list of light metal elements with their densities at 20 ° C:

Period of
the
periodic
system
1
2
3
4th
5
6th
7th
Alkali
metals
Density
in
g / cm³
   
lithium   0.53
sodium   0.97
potassium   0.86
Rubidium   1.53
Cesium   1.90
Francium   1.87
Alkaline earth
metals
Density
in
g / cm³
   
beryllium   1.85
magnesium   1.74
Calcium   1.54
strontium   2.63
barium   3.65
   
Scandium
group
Density
in
g / cm³
   
   
   
Scandium   2.99
yttrium   4.47
   
   
Titanium
group
Density
in
g / cm³
   
   
   
titanium   4.50
   
   
   
Boron
group
Density
in
g / cm³
   
   
aluminum   2.70
   
   
   
   
◈  Where are light metals extracted?
If you would like to see a detailed map of the world on mining "freely movable" in large format (5.6 MB), follow this link

Light metal fires

When extinguishing fires involving light metals, it must be ensured that no water is used. Light metals such as alkali and alkaline earth metals tend to react very violently with water, forming alkali metal hydroxides and releasing hydrogen . In the event of an attempt to extinguish the fire with water, the released hydrogen could ignite and explosions could occur ( oxyhydrogen with atmospheric oxygen). The reactivity of lithium to cesium or beryllium to barium increases sharply. As of potassium, self-ignition occurs .

In addition, many light metals burn, e.g. B. magnesium and aluminum , at very high temperatures. Water decomposes thermally to hydrogen and oxygen, which also leads to an explosive spread of fire.

Water-based extinguishing agents such as extinguishing foam are also prohibited for these reasons. Other extinguishing agents often have no effect on light metal fires, because magnesium continues to burn even in a carbon dioxide atmosphere by removing the oxygen from the carbon dioxide. Normal extinguishing powders are also not suitable for light metal fires.

The following can serve as extinguishing agents:

See also

literature

  • NN Greenwood, A. Earnshaw: Chemistry of the Elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 .

Individual evidence

  1. ^ A b A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1141.
  2. ^ Wissenschaft-Online-Lexika: Entry on light metals in the Lexikon der Chemie , accessed on April 16, 2009
  3. ↑ K. Maile, E. Roos; Materials science for engineers: basics, application, testing. Birkhäuser, 2005, ISBN 978-3-540-22034-3 , p. 10
  4. ↑ Few, older sources give a limit value of <4.5 g / cm³
    J. Elpers, H. Meyer, N. Meyer, H. Marquard, W. Nabbefeld, W. Skornitzke, W. Willner, F. Ruwe: Mechatronik. Elementary level. 4th edition, Bildungsverlag Eins, 2001, ISBN 978-3-8242-2080-9 , p. 52.
    K. Hengesbach: Fachwissen Metall Grundstufe and Fachstufe 1. 4th edition, Bildungsverlag Eins, 1994, ISBN 978-3-8237 -0330-3 , p. 248.
  5. ↑ a b c d e Greenwood / Earnshaw, p. 97.
  6. ↑ a b c d e Greenwood / Earnshaw, p. 136.
  7. ^ Greenwood / Earnshaw, p. 1231.