Question

How is the periodic table arranged?

Answer 1

The number of electrons increases by one as we move from H which is the first element of the modern periodic table. If we go down along a vertical line from H the number of shells are increasing.

Complete step-by-step answer: In the question it is asked to comment on the arrangement of the elements in the periodic table. From the lower classes we are very familiar with the periodic table and after many corrections done over the years the final version of the periodic table which is in use now is called the modern periodic table which was put forward by the scientist Dmitri Mendeleev.
In the modern periodic table the elements are arranged in the increasing pattern of their atomic number. The elements are arranged in a fashion in which the electrons are filled in the shell and the number of electrons increases from one element to another by one unit.
As we know that there are 118 elements and are accommodated in the periodic table. The modern periodic table consists of seven periods and 18 groups. A period is the way of arranging the elements in the horizontal line fashion and the arrangement of elements in a group is the way of arranging the elements from top to down along a vertical line.
The first element in the periodic table is H and it has one electron and one proton and from H electrons are added more to the shells for the other atoms.
For the elements in the specific period the total number of shells present will be equal and for the elements arranged in a specific group, the number of valence electrons will be the same but as we go down the group new shells are introduced in new periods for elements belonging to a group.
So we can conclude that the elements are arranged in a periodic table in accordance with the increasing order of electrons i.e. the increasing order of atomic number, similarity in properties and electronic configuration.

Note: Since the elements in the groups have similar valence electrons they show similar chemical properties.
The right side of the periodic table comprises the non-metals and the left side comprises metals. As the metals are arranged according to the atomic number they show different periodic trends across the periods and groups like ionization enthalpy, electronegativity, electron affinity etc.
The idea of arranging the elements in groups was introduced by the scientist Doberenier and in the early forms of periodic table the elements were put according to the increasing order of atomic mass but it had many drawbacks.