How ionisation energy is inversely proportional to reducing property?
Reducing means gain of electrons, if IE will increase ; it means atom want electrons, not give, right?
So it is directly proportional?!

Understand that reducing potential is not directly related to ionization potential.

Ionization energy or ionization enthalpy is the energy required to remove the most loosely bound electron, that is, the valence electron. Positive IE indicates absorption of energy and vice versa. IE1 is the ionization energy for removal of first electron from the last shell, IE2 is that for removal of second electron after removal of first electron, and so on.

Now, as IE increases, it means that more energy is required to remove an electron. Conversely, as we move across a period (L to R), nuclear charge increases, size decreases, outermost electron is attracted by a greater force, thus IE increases. Similarly, down the group IE decreases.

Now, let's talk about electron gain enthalpy. Electron gain enthalpy(ΔHeg) is the energy absorbed or released per mole upon addition of an electron to the outermost shell of an isolated, gaseous atom. Same rule applies for +ve and -ve ΔHeg as for IE. When we say increase or decrease in ΔHeg, we mean increase or decrease in the modulus value of ΔHeg. For example, -320kJ/mol is lower ΔHeg than -349kJ/mol. As we move across a period (L to R), nuclear charge increases, size decreases, so incoming electron is attracted more towards the nucleus, so ΔHeg increases (more energy is released). Similarly, down the group, ΔHegdecreases (general trend, not accounting exceptions).

Notice that as ΔHeg, increases, reducing potential also increases because the atom with greater ΔHeg will have greater affinity for incoming electrons, thus will reduce more easily. Thus, reducing potential
ΔHeg.

Now that you fully understand IE, ΔHeg and the dependence of reducing potential on ΔHeg, notice that the general periodic trends of IE and ΔHeg are alike. On that basis and that basis alone, we give the empirical relation: IE
ΔHeg.

From the above two relations, we can say that reducing potential
∝ IE.

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