What is Modern Periodic Law?
The modern periodic table is developed after the periodic law and a periodic table given by Mendeleev. In the latter part of the 18th century, Mendeleev made his periodic table. Scientists did not know about the internal structure of the atom back then.
The development of various atomic models and advances in quantum theory revealed that the atomic number is the most basic property of a chemical element. This led to the modification of Mendeleev’s periodic law, which is today called as modern periodic law.
Modern Periodic Law Definition
The modern Periodic law can be stated as:
“The physical and chemical properties of the elements are periodic functions of their atomic numbers”.
The atomic number is equal to the number of electrons or protons in a neutral atom. After knowing the fundamental unit of elements, scientists now had a clear idea about quantum numbers and electronic configuration of elements in the periodic table. After knowing the periodic law, chemists noticed that there is an analogy between the 94 naturally occurring chemical elements. This analogy made people more curious about the chemistry of these elements. Scientists made various artificial elements. A new periodic table was developed based on the modern periodic law by modifying the Mendeleev’s periodic table.
The Modern Periodic Table
The present form of a periodic table that is widely used across the globe is the long form of the periodic table. In this form of a periodic table, the horizontal rows are called periods and the vertical columns are known as the groups.
Groups consist of elements that have similar outer shell electronic configuration in their atoms. Previously the groups were named as IA,…VIIIA, VIII, IB…VIIB and 0. But now they are named as 1, 2, 3…18. In the modern periodic table, periods are the seven horizontal rows. Principle quantum number ‘n’ decides the period of the element. Principle quantum number (n) is one of the four quantum numbers (n, l, m, and s). It tells us about the principle electron shell. For example, if n= 3, then it indicates the principle shell as 3.
Classification of the Elements in the Periodic Table:
Classification of the elements in the periodic table can be done in four ways on the basis of their electronic configurations:
Noble gas elements:
Elements of group 18 of the modern periodic table are considered a noble gas. The electronic configuration of the first element (helium) of this group is 1s2. Rest all the elements (neon, argon, krypton, xenon, and radon) have their outer shell electronic configuration is ns2np6. As the octet of these elements is complete, hence they are highly stable elements.
S-lock and P-block elements come under the category of representative elements. Elements in groups 1 and 2 are known as the s – block elements (elements with 1s2and 2s2 outermost configuration). Group 13-17 are known as the p-block elements (outermost configuration varies from ns2np1 to ns2np5).
Elements which belong to group 3 to 12 and have their outer shell electronic configuration as (n-1)d1-10ns1-2 are referred to as transition elements. These elements are also known as the d-block elements.
Inner transition elements:
Lanthanides and actinides series which falls at the bottom of the periodic table comes under the category of inner transition elements. In these elements the 4f and 5f orbitals are partially filled, rendering them special properties.
1. Who gave the modern periodic law?
Ans: In 1869, Dmitri Mendeleev and Lothar Meyer established the periodic law independently. The first periodic table was developed by Mendeleev and soon followed by Meyer. Each grouped the elements by their mass and proposed regularly reoccurring those properties.
2. Why is the periodic law important?
Ans: Periodic law is recognized as one of chemistry’s most important concepts. While dealing with the chemical elements, their properties, and their chemical reactions, each chemist makes use of Periodic Law, whether consciously or not. The development of the modern periodic table was driven by periodic law.
3. How do periodic trends relate to periodic law?
Ans: Periodic trends are common patterns in the periodic table showing us the various aspects of an element such as electronegativity, atomic radius, or ionizing power. The periodic law tells us that when grouped by atomic number, certain properties of elements occur periodically.
4. Is atomic mass a periodic property?
Ans: Generally, nuclear mass decreases from left to right and always increases from top to bottom. As the atomic number has been developed as the basis for organizing the elements on the periodic table, the atomic number will always increase from left to right and top to bottom.
5. Which is relative periodic property?
Ans: In a given period, the valence shell electronic configuration of any two elements is not the same. Because of this, elements throughout time have different chemical properties with periodic gradation from left to right for their physical properties. This is referred to as periodic property.
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If you still have doubts regarding the periodic law and would like to learn about periodic table class 10, check out our Introduction to the Periodic Table for detailed clarification.