Question

Why is Hydrogen placed in group I of the modern periodic table ?

Answer 1

Hint: Period of the periodic table means the rows which are horizontal of the plane of your page or board. The group of the periodic table means the columns which are vertical to the rows. The elements of a definite row contain the same number of orbits. The elements of the same column have the same chemical behaviors.

Complete step by step answer:
To answer this question, the periodic properties of the elements from different groups should be known. The periodic properties have opposite trends between left to right and top to bottom.
In the periodic table all the elements are arranged by the atomic numbers. Generally, at the left side of the periodic table, elements are metallic in nature. Moving from left to right the metallic character decreases and non-metallic character increases. At the extreme left elements are non-metallic in nature.
Now hydrogen is placed in group one of the modern periodic table. This is because of some similarity of properties of hydrogen with group one elements. The similarities are,
Hydrogen is an electropositive element like other group one elements. It can remove one electron from its outermost shell.
The valency of hydrogen is one the same as group I elements.
Hydrogen can form ionic compounds like other group I elements.
Due to all of these similarities Hydrogen is placed in group I of the modern periodic table.

Note:
There are some limitations of modern periodic table , which are,
-The position of the hydrogen is still in confusion as it has similarities with group 1 and group 17 elements.
-Lanthanides and actinides cannot be placed in the periodic table due to their similar chemical properties.
-There is no such position for the isotopes in the periodic table.