Explain the Pauling method for the determination of ionic radius.

संक्षेप में उत्तर

Ionic radius is defined as the distance from the center of the nucleus of the ion up to which it exerts its influence on the electron cloud of the ion.
Ionic radius of the uni-univalent crystal can be calculated from the inter-ionic distance between the nuclei of the cation and anion.
Pauling assumed that ions present in a crystal lattice are perfect spheres and they are in contact with each other, therefore d = `"r"_("C"^+) + "r"_("A"^-)` …………..(1)
Where, d = distance between the center of the nucleus of cation C⁺ and the anion A^-. `"r"_("C"^+)` = radius of cation and `"r"_("A"^-)` = radius of the anion.
Pauling assumed that the radius of the ion having noble gas configuration (Na⁺ and F^– having 1s², 2s², 2p⁶configuration) is inversely proportional to the effective nuclear charge felt at the periphery of the ion.
i.e. `"r"_("C"^+) α 1/(("Z"_"eff")_("C"^+))` .........(2)
`"r"_("A"^-) α 1/(("Z"_"eff")_("A"^-))` .........(3)
Where Z_eff is the effective nuclear charge
Z_eff = Z – S
Dividing the equation (2) by (3)
`"r"_("C"^+)/("r"_("A"^-)) = (("Z"_"eff")_("A"^-))/(("Z"_"eff")_("C"^+))` ......(4)
On solving equation (1) and (4), the values of `"r"_("C"^+)` and `"r"_("A"^-)` can be obtained.

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अध्याय 3: Periodic Classification Of Elements - Evaluation [पृष्ठ ९७]

अध्याय 3 Periodic Classification Of Elements
Evaluation | Q II. 16. | पृष्ठ ९७

Various successive ionisation enthalpies (in kJ mol^-1) of an element are given below.

IE₁	IE₂	IE₃	IE₄	IE₅
577.5	1,810	2,750	11,580	14,820

The element is

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How does electron affinity change when we move from left to right in a period in the periodic table?

Magnesium loses electrons successively to form Mg⁺, Mg²⁺and Mg³⁺ ions. Which step will have the highest ionisation energy and why?

How would you explain the fact that the second ionisation potential is always higher than the first ionisation potential?

Explain the following, give an appropriate reason.

The electron affinity values of Be and Mg are almost zero and those of N (0.02 eV) and P (0.80 eV) are very low.

Explain the following, give an appropriate reason.

The formation of \[\ce{F^-_{(g)}}\] from \[\ce{F_{(g)}}\] is exothermic while that of \[\ce{O^2-_{(g)}}\] from \[\ce{O_{(g)}}\] is endothermic.

Briefly give the basis for Pauling's scale of electronegativity.