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Hydrogen Element in Periodic Table | Atomic Number Atomic Mass


Hydrogen Element:

Hydrogen is the simplest element in the universe.Its atom has one proton but without neutron in the nucleus. A single electron keeps rotating around the nucleus. Since the number of protons present in the nucleus is the criterion for finding out the atomic number of any element, the atomic number of hydrogen is determined to be one, making it the simplest element in the universe. It does not exist as a single atom but it forms chemical bond with another similar hydrogen atom to form a single molecule.
The electron of a single H atom is present in its s- orbital. The maximum capacity of s- orbital is to hold is two electrons in it. A single hydrogen atom is in a state of high reactivity till it gains one more electron in its s- orbital, reaching the replete and stable configuration. H molecule is relatively more stable than a single hydrogen atom. Nonetheless, hydrogen molecules too are very reactive and undergo chemical reactions with other elements or compounds to form more stable compounds.
Going by the theory of Big Bang, H is the first and foremost primeval substance to come into existence and all other bigger elements have formed by nuclear fusion of multiple hydrogen atoms. It being the lightest element escapes from the earth’s gravity and floats over heavier gases in the atmosphere. Under normal conditions on earth, hydrogen is a colorless, odorless, tasteless, non-toxic, non-metallic, highly combustible diatomic gas.
In the outer space, H exists in neither molecular form nor in combined state,but exists in atomic or plasma state. The proton and electron of hydrogen atom are not together in the state of plasma and they move about actively as highly charged particles. They emit light received from sun and stars. They attain high electrical conductivity as charged particles. It exists in neutral atomic form in interstellar medium.It is the most abundant element in the universe, constituting 90% by number of atoms and 75% by mass.
On the earth’s surface, under normal conditions, H is the third most abundant element.

Industrial Production:

There are many methods of producing H in bulk quantities. One of the cost effective methods is to manufacture H in large quantities by “steam reforming (thermal cracking)” of natural gas. At a temperature range between 700- 1100̊ C, steam or water vapor reacts with methane to form carbon monoxide, liberating hydrogen.

Preparation in laboratory:

Hydrogen can be prepared in laboratory in the following methods: ---
  1. By the action of cold water on highly reactive metals like alkali and certain alkaline earth metals:

The above reactions produce H, forming respective hydroxides liberating a lot of heat. Such reactions are exothermic which give out tremendous amount of heat. In order to reduce the amount of heat generated, amalgams of alkali metals are used as reactants such that a limited portion of metal undergoes reaction resulting in limited quantities of hydrogen and heat.

  1. By the action less active metals with boiling water :

Metals like zinc,  aluminium and magnesium which are less active than alkali metals react in boiling water to produce H, forming the respective metallic oxides.

  1. By the action of steam on very less active metals:

Heavy metals like Fe, Sn and Ni which are still less active than alkali and alkaline earth metals react with steam under high temperature decompose water molecules to liberate hydrogen gas resulting their own metallic oxides.

  1. By Electrolysis of water:

Di hydrogen of high purity is obtained by electrolysis of water in presence of small amount of acid or base because water in neutral medium is a poor conductor of electricity.

  1. From alkalis with amphoteric oxides as bye-product:

Metals such as Be, Zn and Sn react with boiling alkali solution to form hydrogen, along with their respective amphoteric oxides as bye-products.

  1. By action on acids by downward displacement of water:

Metals which are more electropositive than hydrogen i.e., metals which lie above hydrogen in the list of electrochemical series Zn, Fe and Mg react with dilute mineral acids to produce hydrogen gas collected in an inverted glass jar over a beehive shelf, by downward displacement of water into a glass trough. Acids like HCl form respective metal chlorides, H2SO4 form metal sulphates as subsidiary products.

Uses of Hydrogen Element:

Hydrogen is used mainly

  1. as a reducing agent
  2. in hot air balloons
  3. in preparation of heavy water D2O with its isotope as a reactant
  4. in hydrogenation of fats and oils
  5. as a rocket fuel
  6. in welding metals
  7. In commercial fixation of nitrogen from air in Haber Ammonia process.


Hydrogen exists in three different isotopic forms. The atoms of H isotopes exhibit three different mass numbers 1, 2 and 3. If there is a single neutron in its nucleus, the atom is called protium; if there are two neutrons in the nucleus, the atom is called deuterium and if there are three neutrons in the nucleus, the atom is called tritium. The isotope of hydrogen called Protium is more reactive than deuterium. The third isotope of hydrogen, known as tritium, is radioactive in nature.


Hydrogen Element Information:

Discovery year: 1766

Discovered by: Robert Boyle (some believe that Henry Cavendish discovered it)

Atomic number: 1

Relative atomic mass: 1.00784, 1.00811

Electron configuration: 1s1

Block: s-block

Other elements in the same block

Helium, Lithium, Beryllium, Sodium, Magnesium, Potassium, Calcium, Rubidium, Strontium, Caesium, Barium, francium and Radium are other elements in the s-block.

Period: Period 1

Other elements in the same period

Helium is the element in the same period

Group:group 1

Other elements in the same group

Lithium, Sodium, Potassium, Rubidium, Ceasium, Francium are other elements in the same group

Other elements in the same orbital

Allotropes: none

Key isotopes: 1H, 2

Melting point: 13.99 K ​ (−259.16 °C, −434.49 °F)

Boiling point:20.271 K (−252.879 °C, −423.182 °F)

Element category: diatomic non-metal

Density (g cm−3): 0.000082

CAS number: 1333-74-0

Color: colorless

You can know detailed information for each element,

Hydrogen, HeliumLithiumBerylliumBoronCarbonNitrogenOxygenFluorine,  Neon , SodiumMagnesiumAluminiumSiliconPhosphorusSulfurChlorineArgon, PotassiumCalciumScandiumTitaniumVanadiumChromiumManganeseIronCobaltNickelCopperZincGalliumGermaniumArsenicSeleniumBromine, Krypton,  Rubidium, StrontiumYttriumZirconiumNiobiumMolybdenumTechnetiumRutheniumRhodiumPalladiumSilverCadmiumIndiumTinAntimonyTelluriumIodine, Xenon,  Caesium, BariumLanthanum,  CeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercuryThalliumLeadBismuthPoloniumAstatine, Radon,  Francium, RadiumActiniumThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrenciumRutherfordiumDubniumSeaborgiumBohriumHassiumMeitneriumDarmstadtiumRoentgeniumCoperniciumNihoniumFleroviumMoscoviumLivermoriumTennessine, Oganesson.

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