Three elements A,B and C have atomic number 7,8 and 9 respectively.What would be their positions in the modern periodic table mention group and period.Arrange A,B and C in the decreasing order of their size.Which one of the three elements is most reactive and why?

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Solution

a) Position of A = 15th group, 2nd period
Position of B = 16th group, 2nd period
Position of C = 17th group, 2nd period
(b) A>B>C
© C is most reactive as it has smallest size, so it can easily gain electrons.

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Question 33
Three elements A, B and C have 3, 4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, give their valencies.

Q. (a) What were the two major shortcomings of Mendeleev's periodic table? How have these been removed in the modern periodic table?
(b) Two elements X and Y have atomic numbers 12 and 16 respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be formed between them and why?
(c) To which groups of the modern periodic table do the elements X and Y belong? Give reason for your answer.
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Question 4
Which of the following statement(s) about the Modern Periodic Table are incorrect?

(i) The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic number

(ii) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses

(iii) Isotopes are placed in adjoining group (s) in the Periodic Table

(iv)The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number

(a) (i) only
(b) (i), (ii) and (iii)
(c) (i), (ii) and (iv)
(d) (iv) only

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Three elements A,B and C have atomic number 7,8 and 9 respectively.What would be their positions in the modern periodic table mention group and period.Arrange A,B and C in the decreasing order of their size.Which one of the three elements is most reactive and why?

a) Position of A = 15th group, 2nd period Position of B = 16th group, 2nd period Position of C = 17th group, 2nd period (b) A>B>C © C is most reactive as it has smallest size, so it can easily gain electrons.

a) Position of A = 15th group, 2nd period
Position of B = 16th group, 2nd period
Position of C = 17th group, 2nd period
(b) A>B>C
© C is most reactive as it has smallest size, so it can easily gain electrons.