IONIZATION ENERGY

IONIZATION ENERGY:-

   The minimum energy required to remove an electron from its gaseous atom to form an ion is called ionization energy and the process is called ionization. For example

Ionization energy is the energy required to remove electron from gaseous atom because in gaseous state atoms and ions are isolated and are free from external influence and all the energy is utilized to remove electron and no energy is used to overcome force between atoms or ions. Thus we can also say that ionization energy is the quantitative measurement of the stability of an isolated gaseous atom. The energy required to remove first electron is called first ionization energy whereas the amount of energy required to remove second electron is called second ionization energy.

FACTORS INFLUENCING IONIZATION ENERGY:-

•   ATOMIC SIZE:-

             Ionization energy decreases with in increase in atomic size that is 
                     

• EFFECTIVE NUCLEAR CHARGE:-

            Ionization energy increases with increase in effective nuclear charge that is
                                 

• SHIELDING EFFECT:-

            Greater the shielding effect lesser is the ionization energy that is
                                     

• NATURE OF ORBITAL:-

                 Ionization energy also depends upon nature of orbital that is whether it is s-orbital or it is p-orbital or any other. Ionization energy for electrons in the s- orbital is maximum then p-orbital then d-orbital and in the end for f-orbital. The decreasing order of ionization energy for orbital is shown below  s>p>d>f

VARIATION OF IONIZATION ENERGY IN PERIODIC TABLE:-

   Ionization energy increases from left to right in a period and decreases from top to bottom in a group of a periodic table. 

The increase in ionization energy from left to right in a period is due to increase in effective nuclear charge (Protons) till maximum value reached at the end of the period. As a period start with an element having one electron in a valance shell and ends with completion of valence shell. The increase in atomic number is associated with increase in nuclear charge as we move from left to right in period number of protons increases which leads to strong force of attraction, ultimately results in difficult removal of electron. In group due to increase in shells ionization energy decreases instead of the increase in number of protons or nuclear charge. This is due to successive addition of electronic shell as a result of which valence electrons are place at a greater distance from nucleus and according to coulombs law force of attraction is inversely proportional to square of radius from the charge that is

as a result of which electrons are easily removed with less energy. Moreover force of attraction also decreases due to increase in shielding effect.

ABNORMAL TREND OF IONIZATION ENERGY:-

     Ionization energy of group III-A and VI-A elements show abnormal behaviour for example "Be" of group II-A should have ionization energy less than "B" of group III-A but "Be" has greater ionization energy than "B". This is due to electronic configuration Boron(B) that is

as it is partially filled and it is easy to remove electron whereas Be has completely filled s-orbital and thus it is stable than B. Similar is the case with elements of VI-A "O" of group VI-A should have greater ionization energy than "N" of group V-A but "O" has less ionization energy than "N" as in Oxygen electronic configuration is 

one electron can easily be removed to make p-orbital half filled and ultimately more stable where as in N p-orbital is is half filled and it is stable and more energy is required to remove it hence ionization energy is higher.

HIGHER IONIZATION ENERGIES:-

   The amount of energy required to remove an electron after removal of first electron is called second ionization energy and it is always greater than first ionization energy this is because greater nuclear pull is applied on the remaining electrons. For example

similarly energy required to remove third electron is called third ionization energy and it is               7730 KJ/mol for Mg. This show that ionization energy value undergo increase with increase in number of electron to be removed. The reason is same that after removing electron remaining electron are being pulled by greater force. Ionization energy is index to the metallic character. Elements with low ionization energies are metal and those with high ionization energy are non-metals and those with intermediate values are metalloid.

   Gap in first, second, third and higher ionization energies helps us to guess the valency of an element. If there is sufficient gap between first and second ionization energy then element show valency of one and so on.