| 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 |
|
