Helium: Difference between revisions
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imported>Pat Palmer (adding Seealso template aimed at Benchmark quantities) |
imported>Pat Palmer (linking to Benchmark_quantities#Density) |
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'''Helium''' is a [[Chemical elements|chemical element]], having the [[chemical symbol]] He. Its [[atomic number]] (the number of [[proton]]s) is 2. It has a [[Atomic mass#Standard atomic weights of the elements|standard atomic weight]] of 4.002602 g•mol<sup> −1</sup>, and is typically found as a [[gas]] in its elemental form. | '''Helium''' is a [[Chemical elements|chemical element]], having the [[chemical symbol]] He. Its [[atomic number]] (the number of [[proton]]s) is 2. It has a [[Atomic mass#Standard atomic weights of the elements|standard atomic weight]] of 4.002602 g•mol<sup> −1</sup>, and is typically found as a [[gas]] in its elemental form. | ||
Helium is a monatomic noble gas. At a [[pressure]] of 101.325 k[[Pascal (unit)|Pa]], it has a [[boiling point]] of -268.93 °[[Celsius (unit)|C]], and a [[melting point]] of -272.2 °C. | Helium is a monatomic noble gas. At a [[pressure]] of 101.325 k[[Pascal (unit)|Pa]], it has a [[boiling point]] of -268.93 °[[Celsius (unit)|C]], and a [[melting point]] of -272.2 °C. It is of relatively low density--see [[Benchmark_quantities#Density|Benchmark quantities]]. | ||
==Isotopes== | ==Isotopes== | ||
The helium atom has two stable [[isotope]]s, <sup>3</sup>H and <sup>4</sup>He. | The helium atom has two stable [[isotope]]s, <sup>3</sup>H and <sup>4</sup>He. | ||
Revision as of 08:51, 9 December 2020
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Helium is a chemical element, having the chemical symbol He. Its atomic number (the number of protons) is 2. It has a standard atomic weight of 4.002602 g•mol −1, and is typically found as a gas in its elemental form.
Helium is a monatomic noble gas. At a pressure of 101.325 kPa, it has a boiling point of -268.93 °C, and a melting point of -272.2 °C. It is of relatively low density--see Benchmark quantities.
Isotopes
The helium atom has two stable isotopes, 3H and 4He.