Modern Periodic Table: Classification & Periodicity of 118 Elements

Modern Periodic Table is used in order to organize all the known elements. Elements are arranged in the table based on increasing atomic number, electron setup, and persistent chemical properties. Each element is represented by its chemical symbol in the modern periodic table. The number above each symbol is its atomic number.

• Dmitri Mendeleev is the father of the modern periodic table.
• It is known as the periodic table as the elements are arranged in it in rows and columns.
• The horizontal rows from left to right are known as 'periods' while the vertical columns from up to down are known as 'groups'.

Read More: Periodic Classification of Elements

Key Terms: Long Form of Periodic Table, Modern Periodic Table, Mendeleev’s Periodic Table, Electronic Configuration, Atoms, Metals, Non-Metals, Metalloids

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Modern Periodic Table

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Modern Periodic Table is the tabular arrangement of the elements in increasing order of their atomic numbers. It is commonly referred to as the Long Form of the Periodic Table and is based on modern periodic law.

• The elements in the Modern Periodic Table are arranged in a tabular form wherein there are 18 Groups (vertical columns) and 7 Periods (horizontal rows).
• A row is called a period while a column refers to a group.
• In the Modern Periodic Table, the first 94 elements are naturally occurring.
• Whereas the rest of the elements from 95 to 118 have only been synthesized in labs or developed in research centres or atomic reactors.
• The elements in the same group of the Modern Periodic Table have the same valence electron configuration and thus have similar chemical properties.
• The elements in the same period of the Modern Periodic Table will have an increasing order of valence electrons. 
• The modern Periodic Table is the modified and improved version of the various arrangement or models developed by various scientists.
• Dimitri Mendeleev developed the periodic table.
• Henry Moseley, an English physicist, perfected the periodic table in 1913, improving on all the flaws of the Mendeleev table.

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Modern Periodic Law

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According to the Modern Periodic Law given by Henry Moseley – 

The physical and chemical properties of the elements are the periodic functions of their atomic numbers and not their atomic masses. 

The elements in the modern periodic table have been arranged in increasing order of their atomic numbers from left to right across each row. And it has been discovered that the elements having similar properties repeat after regular intervals.

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Periods in the Modern Periodic Table

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The rows in the modern or long form of the periodic table are referred to as periods. Each period of the periodic table represents the number of shells or energy levels present in an atom of an element. 

• There are a total of 7 periods in the Modern Periodic Table that are numbered as 1, 2, 3, 4, 5, 6 and 7 from top to bottom.
• The number of elements in each period varies. The 1st period has only two elements which are Hydrogen and Helium.
• The 2nd and 3rd period of the table consists of 8 elements each while the 4th and 5th period consists of 18 elements each. 
• There are 32 elements in the 6th period of the periodic table and the 7th period also has 32 elements. 
• There are four new elements in the 7th period of the periodic table which are 113 (Nihonium), 115 (Moscovium), 117 (Tennessine), and 118 (Oganesson). 
• Apart from that, there is a separate panel at the bottom of the long form of the periodic table that consists of 14 elements from the 6th period called the lanthanoids and 14 elements from the 7th period called the actinoids.

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Groups in the Modern Periodic Table

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The vertical segments, i.e, the columns in the modern or long form of the periodic table are known as Groups. The elements in a similar group generally show patterns in atomic radii, ionization energy, and electronegativity. The atomic radii of the elements increase from the start to finish in a group. 

• There are 18 groups in the long form of the periodic table that are numbered from 1 to 18.
• Each group in the periodic table consists of elements that have the same outer shell electronic configuration.

What is the Cause of Periodicity in the Modern Periodic Table?

The repetition of the similar outer electronic configuration after certain regular intervals is the cause of periodicity in properties.

• Like, for instance, all the elements of Group 1 have a similar outer electronic configuration, ns¹, where n refers to the Principal Quantum Number of the outermost shell.
• Similarly, the elements of Group 17 have a similar outer electronic configuration, ns²np⁵. They are halogens and hence have similar properties to one another.
• Another instance is that the elements of group 18 have an outer electronic configuration of ns² np⁶. All these elements have fully filled orbitals and this group comprises non-reactive elements called Inert gases. 

Also, we know that the elements in a group in the periodic table have similar properties to the other members of the same group as they all have a similar electron configuration of the outer shell. The periodic table is divided into s, p, d and f blocks on the basis of the entry of the valence electrons in the respective sub-shell.

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Classification of Elements in the Long Form of Periodic Table

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The major classification of elements in the long form of the periodic table or the modern periodic table is described below: 

• Alkali and Alkaline Earth Metals: The initial two groups on the left side of the modern periodic table comprise highly reactive elements except for hydrogen. The elements in the first group contain one electron in the valence shell while the elements in the second group contain two electrons in their valence shell.
• Transition Metals: These transition metals are the elements that occupy the centre of the periodic table and display the properties of metals majorly. The transition metals are the elements starting from Group 3 to Group 12. A few transition metals, known as Lanthanides and Actinides, are placed separately in two rows at the bottom of the periodic table. 
• Metalloids and Non-Metals: In the periodic table, metalloids appear in a diagonal line on the right side and are basically the elements that separate the metals and nonmetals in the periodic table. Metalloids are those elements that exhibit the properties of both metals and non-metals.
• Noble Gases: Noble Gases occupy the extreme right side of the periodic table and are placed in the 18th Group and have completely filled valence shells. These gases are non-reactive and are also called inert gases.

The study of the elements would have been impossible without the existence of the long form of the periodic table or the modern periodic table as the classification of elements in this way helps in the easier understanding of the properties of elements.

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118 Elements and Their Symbols and Atomic Numbers

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The modern periodic table of elements is as follows:

Click here for all the elements of the modern periodic table

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Things to Remember

• The Modern Periodic Table is the arrangement of all the known elements as per their increasing atomic number and recurring chemical properties. 
• Henry Moseley, in 1913, reformed all the flaws of the Mendeleev table, that was given by Dimitri Mendeleev, the father of the periodic table.
• The Modern Periodic Law governs the Modern Periodic Table which states that the physical and chemical properties of the elements are the periodic functions of their atomic numbers. 
• The elements in the periodic table are in a tabular arrangement where a row is called a period and a column refers to a group.
• In the modern periodic table, there are a total of 18 Groups and 7 periods. 
• In the Modern Periodic Table, the elements in the same group have the same valence electron configuration and have similar chemical properties.
• The elements in the same period have an increasing order of valence electrons. 

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Important PYQs Related To This Chapter

1. The element with the atomic number 118, will be… (NEET 1996)
2. Which of the following element has the highest ionisation enthalpy… (BITSAT 2019)
3. A certain compound X when treated with copper… (NEET 1994)
4. KF combines with HF to form… (BITSAT 2005)
5. Which of the following has zero net dipole moment… (BITSAT 2019) 
6. In the clathrates of xenon with water…(BITSAT 2019)
7. Which one of the following statements is not correct...M(AP EAPCET 2009)
8. The chief component of cement is… (JIPMER 2000)
9. The molecular electronic configuration of… (BITSAT 2005)
10. Although the details of the structure of monoclinic sulphur… (CBSE CLASS XII)