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-9
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
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Elements with atomic numbers 12 and 38 have the similar chemical and physical properties of calcium.
The electronic configuration of elements with :
Atomic number 12 = 2, 8, 2
Atomic number 19 = 2, 8, 8, 1
Atomic number 20 = 2, 8, 8, 2
Atomic number 21 = 2, 8, 9, 2
Atomic number 38 = 2, 8, 18, 8, 2
Elements with atomic number 12 i.e., magnesium (Mg) and 38 i.e., strontium (Sr) will have similar physical and chemical properties as element with atomic numbers 20 i.e., calcium (Ca).
The element with atomic number 12 has same chemical properties as that of calcium.
This is because both of them have same number of valence electrons (2).
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