NCERT Solution for Class 10 Science Chapter 5
Periodic Classification of Elements
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-92
Questions No-8
How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
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In the modern periodic table, atoms with similar electronic configurations are placed in the
same column. In a group, the number of valence electrons remains the same. Elements
across a period show an increase in the number of valence electrons.
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Modern periodic table is based on the atomic number and atomic number is directly related to the electronic configuration. One can find the group number and period number of an element on the basis of electronic configuration. For example, if an element has 1 or 2 electrons in its outermost shell, then it would belong to group 1 or group 2. And if it has 3 or more electrons in its outermost shell, then it would belong to group 10 4- the number of electrons in the outermost shell.
All the alkali metals have one electron in their outermost shell, so they are placed in group 1. Thus, all the group 2 elements have 2 electrons in their outermost shell. In group 15 elements, there are 5 electrons in their outermost shell. Similarly, the number of shells in an element indicates its period number. For example, the atomic number of magnesium is 12 and its electronic configuration is 2, 8, 2. Thus it is an element of 3rd period.
Electronic configuration of an element gives the information of valence electrons and number of shell present in the element.
We get the information of group number after knowing valence electrons.
Number shell present in an element is equal to period number.
Thus, by knowing electronic configuration we know the group number and period number of an element, which is the position of element in periodic table.