NCERT Class XI Chemistry Structure of Atom Solutions
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Question : 23
Total: 67
(i) Write the electronic configurations of the following ions :
(a)H –
(b)N a +
(c)O 2 –
(d)F –
(ii) What are the atomic numbers of elements whose outermost electrons are represented by
(a)3 s 1
(b)2 p 3
(c)3 p 5
(iii) Which atoms are indicated by the following configurations?
(a)[ H e ] 2 s 1
(b)[ N e ] 3 s 2 3 p 3
(c)[ A r ] 4 s 2 3 d 1
(a)
(b)
(c)
(d)
(ii) What are the atomic numbers of elements whose outermost electrons are represented by
(a)
(b)
(c)
(iii) Which atoms are indicated by the following configurations?
(a)
(b)
(c)
Solution:
(i) The respective electronic configurations are :
(a)H – 1 s 2
(b)N a + 1 s 2 2 s 2 2 p 6
(c)O 2 – 1 s 2 2 s 2 2 p 6
(d)F – 1 s 2 2 s 2 2 p 6
(ii) (a)3 s 1 1 s 2 2 s 2 2 p 6 3 s 1
∴ The atomic number of element = 11
(b)2 p 3 1 s 2 2 s 2 2 p 3
∴ The atomic number of element = 7
(c)3 p 5 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5
∴ The atomic number of element = 17
(iii) (a)[ H e ] 2 s 1
(b)[ N e ] 3 s 2 3 p 3
(c)[ A r ] 4 s 2 3 d 1
(a)
(b)
(c)
(d)
(ii) (a)
∴ The atomic number of element = 11
(b)
∴ The atomic number of element = 7
(c)
∴ The atomic number of element = 17
(iii) (a)
(b)
(c)
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