CHAPTER - 9 HYDROGEN

POSITION OF HYDROGEN IN THE PERIODIC TABLE

• Electronic Configuration of Hydrogen 1s1
Position of hydrogen in the periodic table: Position of hydrogen in periodic table is not justified because it resembles both alkali metals as well as halogens.

• Resemblance of Hydrogen with Alkali Metals
(i) Electronic Configuration: Hydrogen has one electron in its valence shell like alkali metals.

H → H+ + e-

Na → Na+ + e-

(ii) Both hydrogen and alkali metals form unipositive ions.
For example,
Na → Na+ + e
H → H+ + e
(iii) Hydrogen and alkali metals both shows +1 oxidation state.
(iv) Hydrogen as well as other alkali metals acts as reducing agents.
(v) Both have affinity for electronegative element For example, Na2O, NaCl, H20, HCl.

• Resemblance with Hologens
(i) Electronic configuration: Hydrogen and halogen family both require one electron to fulfil the inert gas configuration

H-1s1 ; He-1s2

X-ns2np5 : Ne-1s22s22p6

(ii) Ionisation energy of hydrogen is almost similar to halogens.
(iii) Hydrogen as well as halogens are Diatomic in nature.
(iv) Many compounds of hydrogen as well as of halogens are of covalent nature.
For example, CH4, SiH4CCl4, SiCl4