Classification of Elements and Periodicity in Properties: Genesis & Types

Classification of Elements and Periodicity in Properties is an essential aspect since many elements are present today. In the 19th century, the discovery of a large number of elements took place, and studying them became very difficult.

• Scientists discovered ways to classify the elements based on their characteristics in a periodic manner.
• Dobereiner’s Triads and Newland’s Octaves are used for classifying the elements.
• Classification of Elements and Periodicity in Properties help study about the periodic table.
• It will help explain the consequence of the electronic configuration of an atom.
• In this, elements are divided into groups with their separate set of properties.
• The properties of elements depend upon the valency and number of shells of an atom.
• Classification of Elements and Periodicity in Properties noted a similarity in the properties of elements.

Key Terms: Classification of Elements and Periodicity in Properties, Classification of Elements, Elements, Periodic Table, Modern Periodic Table, Dobereiner’s Triads, Newland’s Octaves Atomic Mass, Nomenclature, s Block Elements

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Genesis of Periodic Classification

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Given below are the names of the chemists who identified various methods to classify elements in order to make the process of studying those elements easier along with their drawbacks:

Dobereriener’s Triads

A German chemist, Johann Dobererierners identified several groups of three elements which are known as triads. It has similar types of physical and chemical properties.

• He indicated that when triads were arranged in a form of an increasing atomic mass.
• In such cases, the atomic mass of the central element is approximately the mean of atomic mass of first and third elements.
• It was also known as Law of Triads.
• The main drawback is that it is limited to a few triads only.

The below table showcase the Dobereriener’s Triads Theory

Newlands Law Of Octaves

Newland Law of Octaves law states that whenever elements are arranged in ascending atomic masses, then the eighth and the first elements will show the same property.

• This law is even similar to a musical note.
• The theory was proposed by English scientist John Newlands in 1866.
• He arranged approximately 56 elements in increasing order of atomic mass.
• It is also known as the Law of Octaves and important law in the field of chemistry.
• The periodicity of two elements that have an interval of seven elements are similar.

Limitations of Newlands Law of Octaves

The limitations of newlands law of octaves are as follows:

• With the discovery of noble gases, their inclusion led to the disturbance in the overall arrangement.
• The success of this law is limited only to calcium.

Mendeleev's Periodic Table

The Mendeleev periodic table is based on the periodic law. He arranged all the elements in ascending order as per their atomic mass. Mendeleev used an elaborative way to define the physical and chemical properties of the elements.

• The vertical rows in the periodic table are defined as groups.
• Horizontal rows are known as periods.
• He left places for elements that were not even discovered.
• The periodic law states that the chemical and physical properties of any element act as a periodic function to their atomic mass.
• The table helps to study the properties and atomic mass of elements in a systematic way.

Limitations of Mendeleev's Periodic Table

Some of the limitations of mendeleev’s periodic table are as follows:

• Wrong allocation of positions to isotopes of a particular element.
• The positioning of Hydrogen in Mendeleev's Periodic Table is controversial.
• According to law two elements must reflect similar characteristics.
• However the elements present in two sub-groups of one single group fail to reflect similar properties.
• In certain cases elements reflecting similar properties are positioned in two different groups.

In some cases, the elements having higher atomic masses are placed ahead of elements having less atomic mass, which contradicts the law.

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Modern Periodic Law 

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Modern Periodic Law states that elements' physical and chemical properties are periodic functions of their atomic numbers. In the case of a neutral atom, the atomic number is equal to the number of protons or electrons.

• It was created by Mendeleev in the 18th century.
• The value is based on the mass of protons and neutrons present in the nucleus of its atom.
• Elements with different electronic configurations possess different chemical properties.
• The periodicity depends upon the repetition of similar outer shell electronic configurations.
• It is also known as the long form of the periodic table.
• There are seven periods.

Classifcation of elements in the Modern Periodic Table

There are four types of elements in the modern periodic table which are as follows:

Noble Gas Elements

Elements that belong to group 18 of the modern periodic table are known as noble gas elements. The electronic configuration of these elements is in the form of 1s².

Representative Elements

Representative Elements are divided into two categories namely s-block elements and P block Elements. Elements that belong to group 1 and group 2 are called s-block elements. 

• Elements that belong to group 13 to group 17 are called p-block elements. 

Transition Elements

Elements that belong from group 3 to 12 with their electronic configuration as (n-1)d^1-10ns^1-2 are referred to as transition elements. It is also known as D block Elements

Inner Transition Elements

Lanthanides and actinides series elements come under the category of inner transition elements. It is called F block Elements.

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Elements: Notation for IUPAC Nomenclature

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The notation for IUPAC nomenclature for elements are as follows:

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Types of Elements

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Elements can be divided into four categories which are as follows:

S block Elements

They belong to Group 1 and 2 and have alkali metals and alkali earth metals.

P block Elements

They belong to Group 13-18 and contain representative and main group elements.

D block Elements

They belong to Group 3-12 and contain transition elements.

F block Elements

They are Lanthanides and actinides(4f and 5f) type of elements and are inner transition metals.

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Periodic Properties and their trends

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Given below are the periodic properties of the elements that depict a clear trend in the periodic table:

Atomic Radius

The atomic radius of an element depicts the size of an atom. It indicates the distance from the center of the nucleus to the boundary created on the nearby shells of electrons.

• If we move from the left side to the right side, the atomic radius starts to decrease as moving from left to right.
• It tends to increase in the atomic number of an element.
• The nuclear charge will increase whereas the number of shells present in an element remains the same.
• If we move from top to bottom in a group, the atomic radius will increase.

Ionization Energy

Ionization energy is the minimum amount of energy that will be required to remove electrons of an isolated molecule or atom. If we move from the left-hand side to the right-hand side in a period, then izonation energy will start to increase.

• Reason is the electronic radius decreases while nuclear charge increases.
• If we move from top to bottom in a group, ionization energy will decrease.

Electronegativity

Electronegativity is known as a tendency of an atom of a chemical element that tends to attract the shared electronics at the time of chemical bond formation. Fluorine is considered one of the most electronegative elements.

• When we move from the left side to the right side, then the electronegativity will increase in the periodic table.
• The nuclear charges will increase in an atom, so its attractive electron will also increase.
• If we move from top to bottom in a group, the electronegativity will decrease.

Valency

Valency is known as the combining capacity of atoms and elements that lie in the same group of the periodic table have similar valency. It indicates the number of electrons present on the outermost shell of the electron.

• If we move from the left side to the right side in a period, then the valency will firstly increase and then it will start to decrease.
• There is hardly any alteration in the valency across, hence elements of a similar group depict a similar valency.

Metallic Characteristics of an Element

Metals comprise more than 75% of all the elements. They usually appear on the left-hand side of the periodic table and are considered as good conductors of heat and electricity.

• As we move from left side to right side in a period, the metallic property of elements will tend to decrease.
• If we move from top to bottom in a group, the characteristics of metal will tend to increase.

Non-Metallic property of an element

Nonmetals are usually placed at the top right corner of the periodic table, they are usually of solid or gaseous nature and considered as poor conductors of both heat and electricity.

• Moving from left side to right,in a period, the properties of the nonmetals will rise.
• If we move from top to bottom in a group, then the characteristics of nonmetals will decrease.

Reactivity of Elements

The reactivity of elements is dependent on the electropositive property of an element. Hence, more the metallic property, more will be the electropositive nature of the element and more will be its reactivity.

• The property starts to decrease on moving from left to the right side, the reactivity also decreases and vice versa for non metallic elements.

Melting and Boiling Point of Elements

In case of metals the melting and boiling points decrease on moving from top to bottom in a periodic table, whereas, it increases in case of nonmetallic elements.

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Things to Remember

• Classification of Elements and Periodicity in Properties help study about periodic law and periodic table.
• s,p,d and f are four types of elements.
• The periodic table was based on atomic masses and arranged in seven horizontal rows.
• Non-metals acquire top position in periodic table.
• They have less than twenty elements in series.
• For preparation students can also study Periodic Classification of Elements Revision Notes.
• Individuals can find solutions to problems at NCERT Solutions For Class 11 Chemistry Chapter 3: Classification of Elements and Periodicity in Properties.

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Previous Years Questions

• The smallest among the following ion is:
• Beryllium shows diagonal relationship with aluminium. Which of the following similarity is incorrect ?​
• Chloride ion and potassium ion are isoelectronic. Then :​
• The correct order of electron gain enthalpy with negative sign of F, Cl, Br and I, having atomic number 9, 17, 35 and 53 respectively, is:
• The electronegativity of the following elements is in the order
• In the P3,S2. and Cl− ions, the increasing order of size is
• Which of the following is the most electropositive element?
• According to the law of triads,