Ordnungszahl: |
2 |
Name: |
Helium |
Namensursprung: |
Greek: hêlios (sun). |
Entdeckung: |
1895 by Sir William Ramsey, Nils Langet, P.T.Cleve in Scotland/Sweden |
Beschreibung: |
Light, odorless, colorless, tasteless inert gas.
Second most abundant element in the universe. Sixth most abundant in
the earth's atmosphere. |
Vorkommen: |
Found in natural gas deposits and in the air (5 parts
per billion) Constantly lost to space; replenished by radioactive decay
(alpha particles). |
Verwendung: |
Used in balloons, deep sea diving and welding. Also used in very low temperature research. |
Gruppe: |
Noble Gas |
Atomgewicht: |
4.002602 |
Schmelzpunkt: |
-272.2°C at 26 atmos. |
Siedepunkt: |
-268.934°C |
Dichte bei 293 K: |
0.0001787 g/cm³ |
Aggregatszustand bei Raumtemperatur: |
Gas |
Schalen: |
2 |
Orbitale: |
1s2 |
Valenzen: |
0 |
1. Ionisierungs- potential: |
24.5874 V |
2. Ionisierungs- potential: |
54.416 V |
3. Ionisierungs- potential: |
-- |
Atomradius: |
0.49 Å |
Spezifische Wärme: |
5.193 J/gK |
Verdampfungswärme: |
0.0845 kJ/mol |
Schmelzwärme: |
-- |
Thermischer Ausdehnungskoeffizient: |
-- |
Röntgenemission Energie / Wellenlänge: |
|
KA |
KB |
LA |
LB |
MA |
MB |
|
|
|
eV |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
|
Å |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
|
|
Röntgenabsorption Energie / Wellenlänge: |
|
K |
L-I |
L-II |
L-III |
M-I |
M-II |
M-III |
M-IV |
M-V |
eV |
21 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
Å |
590.407 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Röntgen Fluoreszenz Ausbeute: |
|
KA |
KB |
LA |
LB |
MA |
MB |
|
|
|
|
0% |
0% |
0% |
0% |
0% |
0% |
|
|
|
|
Nuklide: |
|
Anteil |
Gewicht |
Spin |
Halbwertszeit |
Zerfallsmodus |
He3 |
0.00013% |
|
3.016 |
1/2 |
Stable |
He4 |
99.9999% |
|
4.0026 |
0 |
Stable | |