Helium
Representation of Helium
| Helium symbol | He |
| Helium atomic number | 2 |
| Helium atomic mass | 4.003 |
| Discovered by | Sir William Ramsay in London, Per Teodor Cleve and Nils Abraham Langlet. |
What is Helium?
Helium, the lightest of the noble gases, had actually been detected and helium is the only element in the periodic table that was discovered by an astronomer.
- Helium is the element which you can find on the upper right side of the periodic table with atomic number 2. It comes first amongst the family of the noble gases.
- It holds one atomic orbital and was named by Lockyer and Frankland. Its name is derived from the Greek word “Helios” meaning Sun. Scientists knew there is an enormous amount of helium in the Sun before it was discovered.
- Helium falls under inert gas since its outermost electron orbital is full of two electrons. Helium can also be found in lasers, compressed air tanks and coolant in nuclear reactors.
- It holds the lowest boiling and melting points amongst the all other elements. The Nuclear fusion of hydrogen in stars generates a significant amount of helium.
Isotopes
Helium has two known stable isotopes – 3He and 4He. The abundance of helium-3 and helium-4 corresponds to 0.0002% and 99.9998% respectively. This difference in abundances can be observed in the Earth’s atmosphere, where the ratio of 4He atoms to 3He atoms is approximately 1000000:1.
Physical Properties of Helium
| Helium (He) | Physical Properties |
| Melting Point | 0.95 K (or -272.2oC) |
| Boiling Point | 4.222 K (or -268.928oC) |
| Density | 0.1786 g/L at STP; 0.145 g.cm-3 at its melting point |
| Critical Temperature and Pressure | 5.195 K; 0.227 MPa |
| Triple Point | 2.177 K; 5.043 kPa |
| Appearance (at STP) | Colourless gas |
Chemical Properties of Helium
| Helium (He) | Chemical Properties |
| Electron Configuration | 1s2 |
| First Ionization Energy | 2372.3 kilojoules per mole |
| Second Ionization Energy | 5250.5 kilojoules per mole |
| Van der Waals Radius | 140 picometers |
| Enthalpy of Fusion | 0.0138 kilojoules/mole |
Uses of Helium
- The primary use of Helium goes in altitudes research and meteorological balloons.
- It is utilized as an inert protective gas in autogenous welding.
- It is the only cooler capable of declining temperature lower than 15K (-434ºF).
- Helium is also used in the production of germanium crystals and silicon crystals.
- Since it has the ability to diffuse through solids much faster than air, helium is used industrially for pipeline leak detection.
- This element is also used in gas chromatography as a carrier gas.
- Owing to its low melting point, liquid helium has nu
Leave a Reply