He
Helium is the second lightest and second most abundant element in the observable universe.
Physical Properties
| الكتلة الذرية | 4.0026 u |
| الكثافة | 0.0001785 g/cm³ |
| Melting Point | 0.95 K |
| نقطة الغليان | 4.22 K |
| المظهر | Colorless gas |
| State at Room Temp | Gas |
الخواص الكيميائية
| طاقة التأين الأولى | 2372.3 kJ/mol |
| القرب الإلكتروني | -48.0 kJ/mol |
| Oxidation States | 0 |
الخصائص الذرية
| تشكيل الإلكترون | 1s2 |
| نصف قطر الذرة | 31.0 pm |
| نصف قطر التكافؤ | 28.0 pm |
| Van der Waals Radius | 140.0 pm |
اكتشاف
| اكتشفها | Pierre Janssen, Joseph Norman Lockyer |
| سنة الاكتشاف | 1868 |
| الموقع | Guntur, India / London, England |
| Named After | Greek 'helios' meaning sun |
عن Helium
Helium is a colorless, odorless, inert monatomic gas that heads the noble gas series. It has the lowest boiling point of all elements at 4.22 K and can only be solidified under pressure. Helium is formed on Earth through radioactive alpha decay of heavy elements. It was first detected spectroscopically in the Sun before being found on Earth.
Uses & Applications
Cryogenics, MRI machines, party balloons, deep-sea diving gas mixtures, leak detection, and semiconductor manufacturing.
حقيقة مضحكة
Helium is the only element that was discovered in space before it was found on Earth, first observed in the solar spectrum during a solar eclipse in 1868.
النظائر
| Mass Number | الوفرة | نصف العمر | Stable |
| 3 | 0.00000134% | - | Yes |
| 4 | 0.99999866% | - | Yes |
تشكيل الإلكترون
1s2