Chemistry

# Finding the position of elements in the periodic table

To find the position of elements in the periodic table up to atomic number 54  there are several methods, some of them are mentioned below:-

## 1: Finding the block of elements in the periodic table

### s-Block

If there are 1 or 2 electrons in the last principal orbit (n) and 2 or 8 electrons in the orbit (n-1) immediately before the last, then that element will be the s-block.

### p-Block

If the last principal orbit (n) has 3 to 8 electrons and immediately before the last orbit (n-1) has 2 or 8 electrons, then that element will belong to the p-block.

### d-Block

If there are 1 or 2 electrons in the main orbit (n) and more than 8 electrons in the orbit (n-1) immediately before the last, then that element will be of the d block. ## 2: Finding the Period of the Elements in the Periodic Table

The number of total orbits used in an element’s electronic configuration is the period number of that element.

## 3: Finding the Groups of the Elements in the Periodic Table

### a) To find the group of elements of s-block

If there are one or two electrons in the last principal orbit of an element, then that element will be of first or second class respectively.

### b) To find the group of elements of p-block

If there is an electron in the last head orbit of an element from 3 to 8 then the group of that element = 10 + electrons of the last orbit.

### c) Finding the group of elements of a d-block

There are two methods to find the group of elements of a d-block, by the first method, the atomic numbers from 39 to 48 can be determined by the second method and the atomic numbers from 39 to 48 by the second method.

The first method (for elements from atomic numbers 21 to 30):-

Group’s Number = Atomic Number (Z) – 18

The second method (for elements from atomic number 39 to 48):-

Group’s Number = Atomic Number (Z) – 36

## Trick method of finding period and group’s no of elements in the periodic table:

This is a very simple method of finding the period and group’s no. of elements of any block but it requires that the order of groups, the atomic number of elements and number of elements in each period, and the position of the classes should be known. The only trick in this is that we have to proceed from the beginning according to the atomic number of the respective element based on the number of elements in the period. Because this periodic table is based on the atomic number or electronic configuration of the elements, and only one group for each atomic number is determined.

For example

if you want to find the period and group’s no. of Manganese (Mn) whose atomic number is 25,

then we know that,

elements in the first period= 2

elements in the second = 8 and

elements in the third period = 8.

The total number of elements in these three periods is 18. It is clear that manganese will be in the fourth period. Now after taking 18 out of 25, we get the number 7. Now in the fourth period from the left side, manganese will come in the seventh group.

Another example:

If you want to find the period and group number of the Phosphorus (P) element, first of all, depending on the number of elements in each period, we know that phosphorus whose atomic number is 15 will come in the third period because 2 in the first period And the second period has 8 elements. Now it becomes clear that it will be located in group number 15 in the order of position of the squares in the third period. Similarly, by this method, we can find the period and group number of any element.