Question
Question: How would you explain the ionization energy trend?...
How would you explain the ionization energy trend?
Solution
We know that for successive ionization energy there must be an increase in a magnitude because of the number of electrons which leads to repulsion and continuous steady decrease. This curve is not a smooth curve as it is a high jump in ionization energy after the atom has lost its valence electron. An atom which has similar electronic configuration as of a noble gas which is
going to hold to its electron. The amount of energy needed to remove an electron beyond valence electrons is significantly greater than the energy of chemical reaction along with their bonding. Thus they only have the valence electrons that are electrons outside of noble gas nucleus which are involved in chemical reaction.
The ionization energy of a particular atom depends on the average electron from the distant nucleus and has extremely effective nuclear charge.
Complete answer:
The ionization energy of an atom is the amount of energy required to remove an electron from the gas state to form a provided atom or ion.
1st ionization energy: The energies required to remove higher energy electrons from neutral gas atoms.
For Example:
Na(g) → Na+(g) + e−I1 = 496 kJ/mol
We can see that ionization energy is positive and this is because it requires energy to remove an electron.
2nd ionization energy - The energies require to removal secondary electron from single charged gas cations
For Example:
Na+(g) → Na2+(g) + e−I2 = 4560 kJ/mol
The secondary ionization energy is almost ten time than that of the first, which is usual because the number of electrons causing repulsion is reduced by the time.
3rd ionization energy - The energies required to remove tertiary electrons from double charge gas cation.
For Example:
Na2+(g) → Na3+(g) + e−I3 = 6913 kJ/mol
The tertiary ionization energy is even away bit higher than the secondary.
1st ionization energy decrease down to a group:
Similarly this is because the high energy electrons are on average as well as farther from the nucleus. As the principal quantum number increases vigorously the size of the orbit increases and the electron is easier to remove.
Example:
I1(Na) > I1(Cs)
I1(Cl) > I1(I)
1st ionization energy increase across the period:
Alternative to the group this is because electrons are in the same principal quantum shell and don't easily compensate for a complete shield of increasing nucleus charges of the proton. Therefore electrons are headed even more tightly and require more energy to be ionized.
Example:
I1(Cl) > I1(Na)
I1(S) > I1(Mg)
Note: Ionization energies are the minimum energy required removing electrons from ions or atoms in the gas phase.
Ionization energy exhibits periodicity of the periodic table elements.
The generalized trend for ionization energy to increase from left to right across elements of period and from left to right across period, the atomic radius decreases so electrons are more attracted towards nucleus.