4. Which two electron configurations represent elements that would have similar

Question

4.

Which two electron configurations represent elements that would have similar chemical properties?

(1) 1s22s22p4       (2) 1s22s22p5       (3) [Ar]4s23d5       (4) [Ar]4s23d104p5

A)

(1) and (2)

B)

(1) and (3)

C)

(2) and (3)

D)

(2) and (4)

E)

(3) and (4)

5.

Which of the following make an isoelectronic pair: Cl–, O2–, F, Ca2+, Fe3+?

A)

Ca2+ and Fe3+

B)

O2– and F

C)

F and Cl–

D)

Cl– and Ca2+

E)

None of the above.

6.

Which of the following is the electron configuration of the iron(III) ion?

A)

[Ar]3d5

B)

[Ar]4s13d5

C)

[Ar]4s23d3

D)

[Ar]3d6

E)

[Ar]4s23d9

7.

Which of the following ion has unpaired electrons in its orbitals?

A)

P3–

B)

V5+

C)

Mg2+

D)

Sc2+

E)

S2-

4.

Which two electron configurations represent elements that would have similar chemical properties?

(1) 1s22s22p4       (2) 1s22s22p5       (3) [Ar]4s23d5       (4) [Ar]4s23d104p5

A)

(1) and (2)

B)

(1) and (3)

C)

(2) and (3)

D)

(2) and (4)

E)

(3) and (4)

5.

Which of the following make an isoelectronic pair: Cl–, O2–, F, Ca2+, Fe3+?

A)

Ca2+ and Fe3+

B)

O2– and F

C)

F and Cl–

D)

Cl– and Ca2+

E)

None of the above.

Explanation / Answer

4. (1) 1s2 , 2s2 2p4

(2) 1s2 , 2s2 2p5

(3) [Ar]4s2 , 3d5

(4) [Ar]4s2 , 3d10 , 4p5

It can be seen that, electronic configurations (2) & (4) follow the same trend. The outer electronic configuration is same in both cases. Hence the elements belongs to the same group.

Thus, elements with electron configurations (2) & (4) have similar chemical properties.

5. Number of electrons in the given species are -

Cl- = 18

O2- = 10

F = 9

Ca2+ = 18

Fe3+ = 23

Among the given species, Cl- and Ca2+ have the same number of electrons.

Hence, Cl- and Ca2+ are the isoelectronic species.

6. iron(III) ion

Fe3+ = 23

Electronic configuratiob of Fe3+ ion is given as -

Fe3+ : 1s2 , 2s2 2p6 , 3s2 3p6 3d5

Fe3+ = [Ar] 3d5

7. The electronic configaration of the ions is given as -

(A) P3- : [Ar] = 1s2 2s2 2p6 3s2 3p6

(B) V5+ : [Ar] = 1s2 2s2 2p6 3s2 3p6

(C) Mg2+ : [Ne] = 1s2 2s2 2p6

(D) Sc2+ : [Ar] 3d1

(E) S2- : [Ar] = 1s2 2s2 2p6 3s2 3p6

Hence, Sc2+ have unpaired electron.

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