Atomic Properties of H
- Atomic Number of H
- 1
- Atomic Mass of H
- 1.0080 u
- Electron Configuration
- 1s1
- Electronegativity
- 2.20
- Block
- s-block
- Group
- 1
- Period
- 1
Hydrogen (H) is element 1 on the periodic table. Atomic mass of H: 1.0080 u. H is in period 1, group 1. Melting point of H: 13.99 K.Density of H: 0.00 g/cm³.
You interact with hydrogen every time you drink water or fill up your car
Component of water and all organic molecules. Makes up ~10% of human body mass. Essential for DNA, proteins, fats, and carbohydrates.
Discovered by Henry Cavendish in England, 1766
Name origin: Greek: hydro (water) and genes (generate)
Colorless, odorless gaseous chemical element. Lightest and most abundant element in the universe. Present in water and in all organic compounds. Chemically reacts with most elements. Discovered by Henry Cavendish in 1776.
Hydrogen has 2 naturally occurring isotopes, plus 1 notable radioactive isotope.
| Isotope | Atomic Mass (u) | Abundance | Half-Life | Decay Mode |
|---|---|---|---|---|
| 11H (H-1)Hydrogen-1 isotope | 1.007825032 | 99.99% | — | — |
| 21H (H-2)Deuterium, DHydrogen-2 isotope | 2.014101778 | 0.0115% | — | — |
| 31H (H-3)Tritium, THydrogen-3 isotope | 3.016049278 | 0% | 12.32 years | β⁻ |
Data source: NIH PubChem (aggregated from IUPAC, NIST)
Isotopes of Hydrogen have important real-world applications in science and industry.
3H (tritium), with a half-life of 12.31 years, decays to 3He. The relative variations in n(3He)/n(3H) ratios can be interpreted in terms of elapsed time for dating purposes. The dates of groundwater recharge (water moving downward from the surface), where large amounts of 3H were received from precipitation following thermonuclear bomb test periods, come from the elapsed time since a water mass became isolated from the atmosphere in the time range from the mid-1950s to the present [15].
3H is used for self-luminous exit signs in aircraft and commercial buildings. It is found in luminous dials, gauges, wristwatches, and luminous paints [22]. 2H, in the form of heavy water, is used in CANDU (CANada Deuterium Uranium) nuclear reactors as a moderator and coolant [23].
2H is used for the isotopic labeling of drugs and nutrients to trace their uptake and metabolism in the human body [24], [25]. 2H, in the form of heavy water, is used to study human metabolism. For example, 2H is used in combination with 18O (double labeled water) to measure energy expenditure [26].
Most hydrogen is used in the production of ammonia. Also used in balloons and in metal refining. Also used as fuel in rockets. Its two heavier isotopes are: deuterium (D) and tritium (T) used respectively for nuclear fission and fusion.
Commercial quantities are produced by reacting superheated steam with methane or carbon. In lab work from reaction of metals with acid solutions or electrolysis.
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