Element: Hydrogen
General data
| Element name | Hydrogen |
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| Chemical symbol | H |
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| Atomic number Z | 1 |
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| Year discovered | 1766 |
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| Standard state (25°C) | Gas |
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| Category | Nonmetal |
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| Block | s |
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| Atomic mass | 1.0080 |
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| CPK color | #FFFFFF |
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Physical properties
| Melting point | 13.81 K (-259.34 °C) |
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| Boiling point | 20.28 K (-252.87 °C) |
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| Density | 0.00008988 g/cm³ |
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Energy properties
| First ionization energy | 13.598 eV |
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| Electron affinity | 0.754 eV |
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Atomic structure
| Protons | 1 (Atomic number) |
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| Neutrons (H-1, most abundant isotope) | 0 |
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| Electrons | 1 |
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| Electron configuration | 1s¹ |
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| Oxidation states | +1, -1 |
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| Electronegativity (Pauling) | 2.2 |
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| Atomic radius (van der Waals) | 120 pm |
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Ionization energies - NIST ASD (1 states)
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
