NEET Chemistry Solved Question Paper 2015

Electronic configuration of Fe²⁺ is [Ar]3d⁶ 4s⁰ 
therefore, Number of electrons  = 6
Mg- 1s² 2s² 2p⁶  (6s electrons)
It matches with the 6d electrons of Fe²⁺ 
Cl- 1s² 2s² 2p⁶ 3s² 3p⁵ (11 p electrons)
It does not match with the 6d  electrons of Fe²⁺
Fe- [Ar] 3d⁶ 4s² (6d electrons)

It does not match with the 6d electrons of Fe²⁺
Ne- 1s² 2s² 2p⁶ 3s² 3p ⁶ (6p electrons)
It matches with the 6d electrons of Fe²⁺.
Hence, Cl has 11 p electrons which do not match in number with 6d electrons of Fe²⁺

Ca²⁺ < K⁺ < Ar
 Ar, K⁺ and Ca²⁺ are isoelectronic i.e with the same number of electrons, 18. For isoelectronic species, ionic radii decrease with increases in effective (relative) positive charge. Also Ar, K and Ca belong to the same period.

For a reaction,


So, mostly the product will be present in the equilibrium mixture.

The solubility of the sulphates. The sulphates becomes less soluble as  you fo down the group i.e

Mg> Ca>Sr> Ba

The magnitude of the lattice energy remains almost constant as the size of the sulphate ion is so big that small increase in the size of the cation from Be to Ba does not make any difference. However, the hydration energy decreases from Be²⁺ to Ba²⁺ appreciably as the size of the cation increases down the group. The significantly high solubility of MgSO₄ is due to high enthalpy of solvation on the smaller Mg²⁺ ions.

 ΔG =ΔG⁰+2.303RT log K log Q
At equilibrium when Δ G = 0 and Q = K
 then ΔG = ΔG⁰ +2.303 RT log K = 0

ΔG⁰ = -2.303 RT log K

Isostructural chemical compounds have similar chemical structures.
Isoelectronic terms refer to two atom, ions or molecules that have the same number of valence electrons.


ClO₃^- = SO₃^2-
 Number of electrons
CO₃^2- = 6+2+24 =32
SO₃^2- = 16+2+24 = 32
ClO₃^2- = 17+24+1 = 42
NO₃^2- = 7+2+24 = 33
Hence ClO₃^2- and SO₃^2-  are isoelectronic and are pyramidal in shape.

Angular momentum of electrons in d- orbital is