Class 11 Chemistry - Chapter Structure of Atom NCERT Solutions | :(i) Write the electronic configurations
:(i) Write the electronic configurations of the following ions: (a) H– (b) Na+ (c) O2–(d) F–
(ii) What are the atomic numbers of elements whose outermost electrons are represented by (a) 3s1 (b) 2p3 and (c) 3p5?
(iii) Which atoms are indicated by the following configurations?
(a) [He] 2s1 (b) [Ne] 3s2 3p3 (c) [Ar] 4s2 3d1.
Electronic configuration of an atom is defined as the representation of the position of electrons in the various energy shell & subshells.
Now A negative charge on the species indicates the gain of an electron by it & A positive charge denotes the loss of an electron
(i) (a) H– ion
The electronic configuration of H atom is 1s1.(atomic number = 1)
∴ Electronic configuration of H– = 1s2
(b) Na+ ion
The electronic configuration of Na atom is 1s2 2s2 2p6 3s1.(atomic number = 11)
∴ Electronic configuration of Na+ = 1s2 2s2 2p6 3s0 Or 1s2 2s2 2p6
(c) O2– ion
The electronic configuration of 0 atom is 1s2 2s2 2p4.(atomic number = 8)
∴ Electronic configuration of O2– ion = 1s2 2s2 p6
(d) F– ion
The electronic configuration of F atom is 1s2 2s2 2p5.(atomic number = 9)
∴ Electron configuration of F– ion = 1s2 2s2 2p6
(ii) (a) 3s1
Completing the electron configuration of the element as 1s2 2s2 2p6 3s1.
∴ Number of electrons present in the atom of the element
= 2 + 2 + 6 + 1 = 11
∴ Atomic number of the element = 11(sodium)
(b) 2p3
Completing the electron configuration of the element as 1s2 2s2 2p3.
∴ Number of electrons present in the atom of the element = 2 + 2 + 3 = 7
∴ Atomic number of the element = 7(nitrogen)
(c) 3p5
Completing the electron configuration of the element as 1s2 2s2 2p5.
∴ Number of electrons present in the atom of the element = 2 + 2 + 5 = 9
∴ Atomic number of the element = 9(fluorine)
(iii) (a) [He] 2s1
The electronic configuration of the element is [He] 2s1 = 1s2 2s1.
∴ Atomic number of the element = 3 (lithium , a p-block element)
(b) [Ne] 3s2 3p3
The electronic configuration of the element is [Ne] 3s2 3p3= 1s2 2s2 2p6 3s2 3p3.
∴ Atomic number of the element = 15(phosphorous, a p block element)
(c) [Ar] 4s2 3d1
The electronic configuration of the element is [Ar] 4s2 3d1= 1s2 2s2 2p6 3s2 3p6 4s2 3d1.
∴ Atomic number of the element = 21(scandium , a d block element)
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1 Comment(s) on this Question
11th class chemistry in Q-23 2nd part (c) u give the configuration of 2p5 and in quest. it is 3p5
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