The elements in the periods have consecutive atomic numbers. These horizontal rows of elements in the table are called periods. Under each element, all the other elements with the same number of valence electrons are placed. So, in the periodic table, the elements are arranged in horizontal rows, on the basis of increasing atomic numbers. Therefore, the significance of the modern periodic table is that it relates the periodicity in the electronic configurations of the elements to the periodicity in the properties of the elements.So the properties of elements are repeated as the electronic configurations are repeated. It can be concluded that as the atomic number increases from 3 to 11, the electronic configuration is repeated from 2,1 to 2,8,1.It means that both sodium and lithium has 1 as itвЂ™s valence electron. So as the atomic number increases to 11, which is an atomic number of sodium and electronic configuration is 2,8,1, it has 1 as its valence electron.From the above table, it is clear that lithium has atomic number 3 and electronic configuration 2, 1, so it has 1 as its valence electron (outermost electron).The electronic configuration of the respective elements is shown below. The elements are from lithium to neon and from sodium to argon. Explanation of Modern Periodic Law which is used to construct the Periodic Table.Д¬onsider the electronic configuration of elements which are arranged on the basis of increasing atomic number. Similar chemical properties are shown by the elements having similar electronic configurations. Periodicity in element electronic configurations leads to periodicity in element chemical properties. There is a periodicity in the electronic configurations of elements when elements are arranged on the basis of increasing atomic numbers. This means that if elements are placed in tabular form on the basis of increasing atomic numbers, then the elements with identical properties will appear after regular intervals or periods. вЂњThe properties of elements are a periodic function of their atomic numbers,вЂќ according to the modern periodic law. The modern periodic table arranges the elements according to their atomic numbers. Long before the concept of the atomic number was developed, the basis of the modern periodic table was well established and even used to predict the properties of undiscovered elements. This was primarily due to the lack of development of the concept of atoms being made up of smaller subatomic particles (protons, neutrons, and electrons). Previously the scientists triedВ to arrange the elements, usingВ relative atomic masses. The elements in the modern periodic table are listed in order of increasing atomic number (the number of protons in the nucleus of an atom). Introduction to Arithmetic Progressions | Class 10 MathsД¬hemists have always tried to arrange the elements in a way that reflects the similarities in their properties.Class 10 RD Sharma Solutions- Chapter 2 Polynomials - Exercise 2.1 | Set 2.Arithmetic Progression - Common difference and Nth term | Class 10 Maths.Electric Potential and Potential Difference.Area of a Triangle - Coordinate Geometry | Class 10 Maths.Euclid's Division Algorithm - Real Numbers | Class 10 Maths.Theorem - The tangent at any point of a circle is perpendicular to the radius through the point of contact - Circles | Class 10 Maths.Step deviation Method for Finding the Mean with Examples.Concave and Convex Mirrors - Ray Diagrams, Image Formation, Applications.Section formula вЂ“ Internal and External Division | Coordinate Geometry.ISRO CS Syllabus for Scientist/Engineer Exam.ISRO CS Original Papers and Official Keys.GATE CS Original Papers and Official Keys.

Modern periodic table pdf