Answer / m. k. atal

In the periodic table, the position of hydrogen is
ambiguous. It is because the properties of hydrogen is
similar to:
(a) Alkali metals because its outer electronic
configuration is ns1 which in similar to I Group alkali
metal.
(b) Halogen group because only one electron is required
to complete the outer shell.
(c) Nitrogen group because its outer shell is half
filled like nitrogen family.

Answer / 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

Answer / sana hasan

In the periodic table hydrogen has been placed at the top
of alkali metals in group 1st.
although it is not a member of the group.however its
position is not simply justified because of its
configuration 1s1.It can be placed along with alkali metals
as they too have 1s1 configuration.

however it can be placed along with halogens in group
17.since just like halogens it also require 1 electron to
have configuration of noble gas helium.

Answer / mazhar ullah jamro

hydrogen at the top of group1A and its other place at the
top of group 7A its exact position still remain un decided.
the deiffernt behavour of hydrogen is because of its
simplest atom which possesses asingle positive charge
nucleus and one electron moving around the nucleus

Answer / nawaraj upadhyay

position of hydrogen in periodic
table
1)similarities with alkali
metal
a)electronic cnfiguration:like alkali netals hydrogen
posses 1valence
electron
b)reducing nature:reduces ferrhc salts 2 ferrous like
alkali metals it is reducing
agent
c)during electrolysis like alkali metals it is collected
in cathode when halogen acids are
electrolysed
d)like alkali metals hydrogen has shame affinity towards
non-metal

Answer / sachmilan

because hydrogen need only one atom to fill up its orbit

Answer / mukul

As elements are arranged in the increasing order of their atomic number in the modern periodic table, the position of hydrogen at position 1 is justified.
Elements are not arranged according their properties in the modern periodic table.If we arrange the elements according to their properties, Li must be placed in II group along with Mg because of greater similarities (Diagonal relationship) between two. Similar diagonal relation also observe between Be and Al; B and Si.

According to my view we adopt any system because of its merits and arrangement of elements in periodic meets this requirement. Hence, placement of hydrogen at number 1 seems correct.

Answer / mukul

As elements are arranged in the increasing order of their atomic number in the modern periodic table, the position of hydrogen in group I and period I is justified.

It is true that hydrogen resembles both with alkali metals and halogens in some of their properties but elements are not arranged according their properties in the modern periodic table. The chemical properties of a group are the consequence of similar outer electronic configurations.

If we arrange the elements according to their properties, Li must be placed in II group along with Mg because of greater similarities (Diagonal relationship) between two. Similar diagonal relation also observe between Be and Al; B and Si.

More ever,transition elements have more similarities among themselves even though they are placed in a separate group i.e according to their atomic number from group III to group XII.

A plot of √ν (where ν is frequency of X-rays emitted) against atomic number (Z ) gave a straight line , as per Henry Moseley who formulated modern periodic law. The law was not formulated on the basis of properties of elements.

Keeping in view of above facts, placement of hydrogen in group I and period I seems more appropriate than placing in the center or any other place in the periodic table.

Answer / ana gomez mutolo

The position of hydrogen in the periodic tableis in group
one and period one.It is the alkali group.

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