Chapter - 9 Hydrogen Position of hydrogen in the periodic tableHydrogen means the generator of water. It is the element with simplest atomic structure in nature. There is huge number of compounds formed using hydrogen as constituent. Hydrogen is located in the frst group of theperiodic table. The frst group elements or alkali metals resemble with hydrogen in case of electronic confguration. Hydrogen requires only one electron to gain noble gasconfguration.Hydrogen also resembles with halogens which at the same place require only one electron to gain noble gas confguration.There have been discussions on the positionof hydrogen in the periodic table.Like alkali metals Hydrogen forms halides sulphides and o!ides.It di"ers from alkali metals in case of ioni#ation enthalpy but shows correspondence with halogens.$ihydrogen %ccurrence &. It is the most abundant element inthe universe.'. It is the principle element in solar atmosphere.(. Its free state is in less abundance on earth)s atmosphere due to its lightweight.*. $ihydrogen is mostly found in combined form on earth)s crust. Isotopes of hydrogen&. Three isotopes of hydrogen are +I s ot o pe so fh yd r og enP r o t i u m D e u t e r i u m t r i t i u m'. Protium has no neutron but tritium has two nad deuterium has one neutron.(. Tritium is radioactive and emits ,- particle.Preparation of dihydrogen Laboratory preparation of dihydrogen&. It is usually prepared by the reaction of granulated #inc with dilute hydrochloric acid.'. .eaction of #inc with alkali /aq.0 can also form dihydrogen. 1ommercial Preparation of hydrogen&. 2lectrolysis of acidifed water using platinum lectrodes gives hydrogen.