the tendency of group 15 elements to show -3 oxidation state decreases as we move down the group from N to Bi due to a gradual decrease in the electronegativity and ionisation enthalpy . please explain this statement with respect to the decrease in the electronegativity and ionization enthalpy .
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Electronegativity is the tendency or ability of an atom for gaining an electron from any other atom (on the basis of energy)
For example, Fluorine has 7 valence electrons. It will be easier for it to gain an electron rather than loosing 7. If it looses 7 electrons, it has to accept the equivalent amount of energy which is difficult for it to handle. In case of Oxygen it has 6 valence electrons. It will be easier for it to gain 2 more electrons rather than loosing 6 but if compare to Fluorine, the ability of gaining electron of Fluorine is more than that of Oxygen. So the conclusion is that it is easier for Oxygen to gain 2 electrons but it is more easier for Fluorine to gain 1 electron rather than 2, hence Fluorine is more electronegative than Oxygen
Also while moving down the group, atoms tend to give up electrons more easily due to increasing shell number and hence the electronegativity decreases.
Ionisation enthalpy is the amount of energy required to break a salt molecule into cation and anion (ions).
Ionisation enthalpy for different molecules is calculated experimentally and is fixed.
Now, the question
As I've already told you that how electronegativity decreases as we go down the group.
(Due to increasing shell number, the tendency to loose electron increases and electronegativity decreases)
Also, we know that moving down the group, shell number increases. As shell number increases atoms tend to loose electron very quickly and easily and again easily gains energy due to which small amount of energy is sufficient for atom with more number of shells.
Hence, ionisation enthalpy decrease down the group.
For example, Fluorine has 7 valence electrons. It will be easier for it to gain an electron rather than loosing 7. If it looses 7 electrons, it has to accept the equivalent amount of energy which is difficult for it to handle. In case of Oxygen it has 6 valence electrons. It will be easier for it to gain 2 more electrons rather than loosing 6 but if compare to Fluorine, the ability of gaining electron of Fluorine is more than that of Oxygen. So the conclusion is that it is easier for Oxygen to gain 2 electrons but it is more easier for Fluorine to gain 1 electron rather than 2, hence Fluorine is more electronegative than Oxygen
Also while moving down the group, atoms tend to give up electrons more easily due to increasing shell number and hence the electronegativity decreases.
Ionisation enthalpy is the amount of energy required to break a salt molecule into cation and anion (ions).
Ionisation enthalpy for different molecules is calculated experimentally and is fixed.
Now, the question
As I've already told you that how electronegativity decreases as we go down the group.
(Due to increasing shell number, the tendency to loose electron increases and electronegativity decreases)
Also, we know that moving down the group, shell number increases. As shell number increases atoms tend to loose electron very quickly and easily and again easily gains energy due to which small amount of energy is sufficient for atom with more number of shells.
Hence, ionisation enthalpy decrease down the group.
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