1. Symbol: He
2. Atomic Number: 2
3. Atomic Mass: 4.002602
4. Group: 18 (Noble Gases)
5. Period: 1
6. Block: s-block
7. Electron Configuration: 1s²
8. State at Room Temperature: Gas
9. Melting Point: -272.2°C (-457.9°F) at 2.5 MPa (helium does not solidify at standard pressure)
10. Boiling Point: -268.93°C (-452.07°F)
11. Density: 0.1786 g/L (at STP)
12. Isotopes: Helium-3 (³He) and Helium-4 (⁴He)
13. Most Abundant Isotope: Helium-4 (⁴He)
14. Phase at STP: Gas
15. Color: Colorless
16. Odor: Odorless
17. Taste: Tasteless
18. Flammability: Non-flammable
19. Critical Temperature: 5.2 K (-268.95°C, -452.11°F)
20. Critical Pressure: 0.227 MPa (2.25 atm)
21. Thermal Conductivity: 0.1513 W/(m·K) at 300 K
22. Speed of Sound in Helium: 965 m/s at 27°C (300 K)
23. Reactivity: Inert
24. Uses: Cryogenics, pressurizing and purging systems, gas chromatography, helium-neon lasers, arc welding, breathing mixtures for deep-sea diving
25. Discovery: Discovered in 1868 by Pierre Janssen and Norman Lockyer
26. Abundance in the Universe: Second most abundant element
27. Production Methods: Natural gas extraction, fractional distillation of liquefied air
28. Applications: Cooling superconducting magnets, filling balloons and airships, providing inert protective atmospheres for arc welding, and as a breathing gas in deep-sea diving
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