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How to Find the Group and Period of an Element for JEE

An Introduction to Periodic Table

Last updated date: 20th Mar 2023
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The periodic table helps in the systematic study of the majority of natural elements. In the periodic table, elements are categorized into different groups and periods, which aids in the study of the compounds created by those elements. It is also possible to analyze the ionization energy, electromagnetism, electron affinity, and so on.

For the first time, Mendeleev published the periodic law, stating that "the properties of the elements are a periodic function of their atomic weights.” The present periodic table, which we use today, is an updated version of certain models proposed by scientists in the nineteenth and twentieth centuries. The table is a list of elements arranged in ascending order of their atomic numbers. 

The periodic table in its current form is known as the modern periodic table. It has 18 vertical columns and 7 horizontal rows. The position of elements in the modern periodic table is determined by determining periods and groups in the periodic table. We will discuss how group period and block of elements can be found out using different rules devised. The periodic table with group number and period number is given below:-

Periodic Table with Group Numbers and Period Numbers

Periodic Table with Group Numbers and Period Numbers


The periodic table's horizontal row is called a period. The periodic table is divided into seven periods, each starting on the far left. When a new primary energy level begins to fill with electrons, a new period begins. Period 1 only includes two elements (hydrogen and helium), but periods 2 and 3 each have eight. There are 18 elements in Periods 4 and 5. The two bottom rows have 32 elements belonging to period 6 and 7 hence are separated from the rest of the table. These two rows have been stripped out to make the table fit on a single page more easily. These two rows are kept at the end of the table mainly named as lanthanides and actinides. Elements toward the left side of a period are all metals, while the elements on the right side are generally nonmetals.

How to Find the Period of an Element?

The value of n for the outermost or valence shell is shown by the period. The number of shells in an atom determines the period. The period of an element is represented by the principal quantum number (n) of the valence electrons in the electronic configuration of an atom.

The number of shells equals the number of periods when determining a period.

Example: Na- 2,8,1 - There are three shells, hence the period number is 3.

Calcium - 2,8,8,2 - There are four shells, hence period number is four.


Based on the organization of the outer shell electrons, a group is a vertical column of the periodic table. There are 18 groupings in total. You should be familiar with both of the numbering systems that are often used to designate groups. The letters A and B are used in the conventional system in the United States. 1A and 2A are the first two groups, while 3A through 8A are the last six. The middle groups' names begin with the letter B. In Europe, however, there was a slightly different structure in place. The International Union of Pure and Applied Chemistry (IUPAC) agreed that the official system for numbering groups would be a simple 1 through 18  from left to right approach to avoid misunderstanding. If g is an element of any group and n is some positive integer then the order of an element in a group is given as e=gn.

How to Find Group Number?

To determine the group, we must first know the following rules:

  • The group number is equal to the number of valence electrons if the element is in the s block.
    Example: 2,8,2 Mg(12)
    Valence electrons = group no= 2

  • If the element belongs to the p block, the group number can be calculated using the formula (number of valence electrons + 10), for a group.
    Example: Sulfur (16) - 2,8,6
    Group = no. of valence electrons ie 10 = 6+ 10 = 16

  • If the element is in the d block, the number of electrons in the (n-1)d subshell + no of electrons in (n) s subshell. The group number is determined by this formula.
    Example: Fe(26): $[Ar]3d^64s^2$
    Group = number of electrons in(n−1)d subshell + number of electrons in (n)s subshell = 6+2 = 8

  • The number of the group is always 3 if the element is in the f block, Example: Cerium (58) belongs to the 3rd group in the periodic table.


The periodic table is a table that represents chemical elements in order of increasing atomic number, allowing one to see trends in their properties.

Periods are the seven rows of the periodic table. Metals are located on the left side of the table, whereas nonmetals are located on the right.The columns are referred to as groups. Elements with comparable characteristics are grouped together. As each element gains an electron energy level, the atomic radius grows as it moves down the group. Because adding an electron shell pulls the valence electrons further away from the nucleus, electronegativity falls as you move down a group. Thus in order  to understand the trends and properties groups and period are of great significance 

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FAQs on How to Find the Group and Period of an Element for JEE

1. What are blocks in the periodic table?

The outer electron subshell of the atom is shown by blocks on the periodic table. The first two categories (alkali metals and alkaline earths), hydrogen, and helium form the s-block. Groups 13 to 18 make up the p-block. Groups 3 to 12 are transition metals, and they make up the d-block. The two periods below the main body of the periodic table make up the f-block (the lanthanides and actinides).The type of orbital that receives the last electron correlates to the block of an element.

2. Describe mendeleev periodic table.

Elements were arranged in Mendeleev's periodic table based on their fundamental property, atomic mass, and chemical characteristics. Only 63 elements were known at Mendeleev's time. Mendeleev discovered that the properties of elements were related to atomic mass in a periodic pattern after analyzing their qualities. He ordered the elements in the periodic table so that those with comparable properties were in the same vertical columns. He postulated that:- “The properties of elements are the periodic function of their atomic masses”. Vertical columns in the periodic table and horizontal rows in the periodic table were named groups and periods, respectively, in Mendeleev's periodic table.