Class 10 Science Chapter 5 Periodic Classification of Elements

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Class 10 Science Chapter 5 Periodic Classification of  Elements

Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 10 Science Chapter 5 Periodic Classification of Elements Solutions for All Subjects, You can practice these here…

EXERCISES 

Q.1. Which of the following statements is not a correct statement about the trends when going from left to right across the periods of Periodic table . 

( a ) The elements become less metallic in nature . 

( b ) The number of valence electrons increases . 

( c ) The atoms lose their electrons more easily . 

( d ) The oxides become more acidic . 

Ans :- ( c ) The atoms lose their electrons easily when going left to right is not correct . 

Q.2. Element X forms a chloride with the formula Xcl₂ which is solid with a high melting point . X would most likely be in the same group of the Periodic Table as 

( a ) Na 

( b ) Mg 

( c ) AI 

( d ) Si 

Ans :- ( b ) Mg.

Q.3. Which element has 

( a ) Two shells , both of which are completely filled with electrons ? 

( b ) The electronic configuration 2 , 8 , 2 ? 

( c ) A total of three shells , with four electrons in its valence shell ? 

( d ) A total of two shells , with three electrons in its valence shell ? 

( e ) Twice as many electrons in its second shell as in its first shell ? 

Ans :- ( a ) Ne ( 2, 8 ) 

          ( b ) Mg 

          ( c ) Si (2, 8, 4) 

          ( d ) B (2, 3) 

          ( e ) C (2, 4) 

Q.4. ( a ) What property do all elements in the  same column of the periodic table as born have in common ?  

( b ) What property do all elements in the same column of the periodic Table as fluorine have in common ?  

Ans :- ( a ) They have the same valence and are metalloids.  

( b ) They form acidic oxides and have seven electrons in their outermost shells.  

Q.5.  An atom has electronic configuration 2, 8, 7.

( a ) What is the atomic number of these elements ?  

( b ) To which of the following elements would it be chemically similar ?  (Atomic numbers are given in parentheses) N (7)  F (9)  P (15)  Ar (18) 

Ans :- (a) The atomic number of the element = 2 + 8 + 7                 

                                                                        = 17 

(b) F (9) Because the noof electrons of the outermost shell of F is 7 

Q.6. The position of three elements A, B, and C in the Periodic Table are shown below : 

( a ) State whether A is a metal Or non metal.

( b ) State whether C is more reactive or less reactive that A. 

( c ) Will C be larger or smaller in size than B ? 

( d ) Which type of ion , cation or anion will be formed by element A ? 

Ans :- ( a ) Element A is in group 17. Now , group 17 is on the right side or the periodic table where non – metals are placed . So, element A is a non – metal . 

( b ) In group 17 of halogens , the chemical reactivity decreases on going down in a group . Thus element C will be less reactive than element A. 

( c ) On going from left to right in a period , the size of atoms , decreases . So , the atom of C will be smaller in size than an atom of B. 

( d ) Element A of group 17 has 7 valence electrons . So, it will accept 1 electrons to form a negatively charged ion , A. The negatively charged ion is called anion . Thus , element A will form an anion . 

Q.7. Nitrogen ( atomic number 7 ) and phosphorus ( atomic number 15 ) belong to group 15 of the Periodic Table . Write the electronic configuration A these two elements . Which of these will be more electronegative ? Why ? 

Ans :- Electronic configuration of Nitrogen = 2,5

Electronic configuration of phosphorous    = 2 , 8,5 

Nitrogen will be more electronegative because outermost shell is nearer to nucleus . 

Q.8. How does the electronic configuration of an atom relate to its position in the Modern Periodic Table ? 

Ans :- The position of an atom in the periodic table is related to the number of electrons in the outermost shell. In a given column of group , all elements have the same number of electrons in their outermost shells .

Q.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 ? 

Ans :- The electronic configuration of calcium = 2, 8, 8, 2

The electronic configuration of atomic number 12 = 2 , 8, 2 

The electronic configuration of atomic number 19 = 2 , 8, 8 , 1 

The electronic configuration of atomic number 21 = 2 , 8, 8, 3 

The electronic configuration of atomic number 38 = 2 , 8, 18 , 8, 2 

Elements with atomic number 12 38 will have similar physical and chemical properties as calcium . 

Q.10. Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and Modern Periodic Table . 

Ans :-  

Mendeleev’s Periodic Table	Modern Periodic Table
1. Mendeleev’s periodic table is based on atomic masses of based on atomic number of elements .	1. Modern periodic table is based on atomic number of elements .
2. Mendeleev’s periodic table does not explain the reason for the periodicity in the properties of elements.	2. Modern periodic table says that since the electronic configurations of elements are  repeated at regular intervals therefore , the properties, of elements are also repeated at regular intervals.
3. There are nine vertical columns called groups .	3. There are eighteen vertical columns called groups.
4. Mendeliev’s periodic table had a number of defects .	4. There are no defeats in the  modern periodic table .

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