Answer Posted / zeeshan

Position of an element in periodic table depends upon its
electronic configuration and properties. Hydrogen resembles
the elements of group I-A, IV-A and VII-A in some respects.
Properties of hydrogen do not completely match any one of
the above-mentioned groups. That is why position of hydrogen
is still undecided.
In the coming lines we will discuss why hydrogen can not be
placed in a particular group in the periodic table.

Resemblance Of Hydrogen With Alkali Metals(Group I-A)

1) Like alkali metals hydrogen has one electron in its
valency shell.
Explanation


H (Z=1): K1

Li (Z=3): K2, L1

Na (Z=11): K2, L8, M1

(2) Valance shell electronic configuration of hydrogen
and alkali metal is same.


Explanation

H (Z=1): 1S1
Na (Z=11): 1S2,2S2,2P6,3S1

3) Both hydrogen an alkali metals are good reducing
agents.
4) Like alkali metals hydrogen can also form halides.
Explanation:
Hydrogen:
HCl, HI.
I-A:
NaCl, KBr.
5) Halides of alkali metals and hydrogen ionized in
similar way in aqueous solution.


Explanation:

HCl (aq) è H+(aq) + Cl-(aq)

NaCl(aq) è Na+(aq) + Cl-(aq)



6) Like alkali metals hydrogen can also form compounds with
non-metals.



Explanation:

I-A:

Na2S

Hydrogen:

H2S

[S and Cl are non-metals]



DIFFERENCES :-

1) Hydrogen is a non-metal where as elements of I-A
are metals.
2) Hydrogen can form both covalent and ionic compounds. But
alkali metals only form ionic compounds.
3) Hydrogen cannot lose its valence electron.
4) Hydrogen is a gas at room temperature but alkali metals
are solids.
5) Unlike Na+ or K+ hydrogen ion (H+) is unstable in water.


Explanation:


H+ + H2O è H3O+

6) I.P. of hydrogen is very high as compared to alkali
metals.


Explanation
I.P. of hydrogen is 313 Kcal per mole.
I.P. of alkali metals max. is 147 Kcal per mole.

Resemblance of Hydrogen with Carbon Family (IV-A)
1) Valance shell of hydrogen is half-filled like the
elements of group IV-A.
Explanation:
H (Z=1) : Capacity of K-Shell =2 , no. of
electrons = 1 , % = 50%
C(z=6) : Capacity of L-Shell = 8 , no. of
electrons = 4 , % = 50%

2) I.P. and E.A. of hydrogen and carbon are comparable.
3) E.N. of H and Carbon family are almost similar. [H = 2.1,
C = 2.5 , Si= 2.4]
Explanation
DIFFERENCES
1) Carbon is tetravalent but Hydrogen is a mono-valent.
2) Hydrogen is a gas at room temperature but elements of
group IV-A are solids.
3) Boiling and melting points of hydrogen is very less than
that of the elements of group IV-A.
Resemblance Of Hydrogen With Halogens
1) Both Hydrogen and Halogens require one electron to
complete their valence shell.
2) Both hydrogen and Halogens are non-metals(Except iodine
which has partial metallic character).
3) Both hydrogen and Halogens acts as negative ions when
combined with metals.
4) Their molecules are diatomic.
5) Like Halogens, hydrogen can also form both ionic and
covalent bond.
Explanation
Hydrogen:
NaH (ionic),
CH4 (Covalent)
Halogens:
NaCl (ionic), HCl
6) Both H and Halogens form compound with metals and non-metals.
Explanation
Hydrogen :H2S [S=non-metal]
Halogens : HCl [H = non-metal]
DIFFERENCES
1) Hydrogen has one electron in valence shell while Halogens
has seven electrons.
2) Electronic configuration of H = 1S1,
Valence shell electronic configuration of Halogens = nS2, nS5
3) Unlike X- ion, H- ion is unstable in water and reacts in
the following manner.
Explanation

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