2 He Helium 4,0026 u

Helium

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Periode
1
Golongan
18
Blok
s-blok
Fase (STP)
Gas

Helium is the second lightest and second most abundant element in the universe. It is an inert noble gas used in cryogenics and as a lifting gas.

Penampilan: Colorless gas

About Helium

Chemically inert and second only to hydrogen in lightness, helium fills atomic number 2 with an atomic mass of 4.0026. Its two electrons complete the 1s shell, a closed configuration reflected in an exceptionally high ionization energy of 2372 kJ/mol and the absence of ordinary chemistry. The colorless noble gas remains liquid closer to absolute zero than any other substance, boiling at just 4.2 K. Pierre Janssen first detected it in 1868, in the spectrum of the Sun rather than on Earth. As the second most abundant element in the universe, helium is valued in cryogenics, where its low boiling point is essential, and as a non-flammable lifting gas—both uses resting on the stability that keeps it from bonding. It sits in group 18.

Sifat Fisika

Massa Atom 4.0026 u
Kerapatan 0.0001785 g/cm³
Titik Lebur -272.2 °C
Titik Didih -268.9 °C
Fase pada STP Gas
Jari-jari Atom 31.0 pm

Sifat Elektronik

Energi Ionisasi 2372.3 eV
Elektron Valensi 2

Konfigurasi Elektron

Konfigurasi 1s²

Electron Shell Configuration

Helium electron shell configuration He 2e⁻
Electron shell structure of Helium — electrons per shell.
Shell Electrons
1 (K) 2

Position in Periodic Table

Helium position in the periodic table He

Penemuan

Ditemukan oleh: Pierre Janssen
Tahun: 1868

Blok & Periode

Blok

s p d f

Periode

1 2 3 4 5 6 7

Tabel Periodik

Lantanida Aktinida

Reaksi yang Melibatkan He

Proton-Proton Chain (Solar Fusion)

4¹H → ⁴He + 2e⁺ + 2νₑ + energy

Nuclear

Deuterium-Tritium Fusion

²H + ³H → ⁴He + ¹n

Nuclear

Alpha Decay of Radium-226

²²⁶Ra → ²²²Rn + ⁴He

Nuclear

Alpha Decay of Polonium-210

²¹⁰Po → ²⁰⁶Pb + ⁴He

Nuclear

Alpha Decay of Uranium-238

²³⁸U → ²³⁴Th + ⁴He

Nuclear
Lihat semua 12 reaksi →

Lebih banyak Gas Mulia

10 Ne Neon 18 Ar Argon 36 Kr Krypton 54 Xe Xenon 86 Rn Radon

Explore on Science FYI

StarFYI
Sun (Sol)

Helium produced by hydrogen fusion in stellar cores

Frequently Asked Questions

What is Helium?
Helium (He) is a chemical element with atomic number 2. It is a gas at standard temperature and pressure, classified as a gas mulia.
What are the key properties of Helium?
Helium has an atomic mass of 4.0026 u, density of 0.0001785 g/cm³, melting point of -272.2°C, boiling point of -268.9°C.
What is the electron configuration of Helium?
The electron configuration of Helium is 1s2. It is in the s-block of the periodic table.
Who discovered Helium?
Helium was discovered by Pierre Janssen in 1868.