There are some rules to predict period, group & block in Periodic table. Here, we will classify the elements of the periodic table.
How to predict group in Periodic table
- For s-block elements, group number is equal to the number of valence electrons.
- In case of p-block elements group number is equal to the 10 + number of electrons in the valence shell.
- For d-block elements group number is equal to the number of electrons in ( n – 1 ) d subshell + number of electrons in valence shell.
How to predict period of an element
Period corresponds to the principal quantum number of the valence shell.
How to predict block of an element
The block of an element corresponds to the type of orbital which receives the last electron.
Examples to predict period, group & block in Periodic table
- Element A : 1s2 2s2 2p6
Element A has the valence electron 2p orbital. Therefore, it belongs to p-block element.
Group number = 10 + 8 =18 th group in the periodic table.
Period refers to the principal quantum number of the valence shell : n = 2 which means 2nd period
Element A is the representative element
2. Element B : 1s2 2s2 2p6 3s1
Element B has the valence electron 3s orbital. Therefore, it belongs to s-block element.
Group number = number of valence electrons =1 Therefore, 1st group in the periodic table.
Period refers to the principal quantum number of the valence shell, n = 3 which means 3rd period
Element B is the representative element
Predict the period, group & block of the element in the PT with EC, ( n -1 ) d2 ns2
For n = 4, the EC = (4-1) d1 4s 2 The element corresponds to Ti which is a d-block element.
Group number = Number of electrons in ( n – 1 ) d subshell + number of electrons in the nth shell = 2+2 = 4 th
For n = 4, period = 4th in the PT
Check out the post on what is f-block elements here :
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