Question

The ground state electronic configurations of some elements, A, B, C, D, and E (these symbols represent the some of the known elements given in the Modern periodic table) are as follows :

A : 1s2 2s2 2p6 3s2 3p2

B : 1s2 2s2 2p6 3s2 3p6 4s1

C : 1s2 2s2 2p6 3s2 3p1

D : 1s2 2s2 2p6 3s2 3p6 3d5 4s1

E : 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6.

Match the electronic configurations of the elements with the properties given below and select the correct sequence by choosing the correct codes given.

(i) Element forms a cation which is isoelectronic with P3–.

(ii) Element which in its compounds can show a maximum oxidation state of +6 and also forms coloured compounds in this oxidation state.

(iii) Element has largest atomic radius and highest first ionisation enthalpy in the respective period.

(iv) Element which has intermediate value of electronegativity and its oxide forms salts with strong acids and bases.

• A. B C E A
• B. B D E C
• C. B C D E
• D. A B C D

Answer 1

Answer: (B)

B D E C

Answer 2

(i) Alkali metal, potassium forms K+ (number of electrons = 18) which is isoelectronic with P3– (number of electrons = 18) $\rightarrow$ B.

(ii) Transition element, chromium show maximum oxidation state of +6 in Cr2O72– and CrO42– and they are coloured $\rightarrow$D.

(iii) Noble gas, Kr has largest atomic radius because radius is expressed as Vanderwaal radius and there are interelectronic repulsions due to completely filled outermost shell. Inert gas has highest first ionisation enthalpy in the respective period because of stable valence shell electron configuration $\rightarrow$E.

(iv) Element (Z=13), aluminium has intermediate value of electronegativity and therefore its oxide is amphoteric in nature $\rightarrow$C.