Solution:
The ionization enthalpy, also known as ionization energy, is the energy required to remove the most loosely bound electron from an isolated gaseous atom to form a cation. Generally speaking, ionization enthalpy increases across a period from left to right in the periodic table and decreases down a group. This is because the effective nuclear charge (which refers to the net positive charge experienced by an electron in a multi-electron atom) increases across a period, pulling the electrons in closer and thus requiring more energy to remove an electron. Conversely, ionization enthalpy decreases down a group as the outermost electrons are farther from the nucleus and more shielded by inner electrons, which makes them easier to remove.
Let's examine the given options in the context of their positions in the periodic table:
Titanium (Ti) - Atomic number 22 , located in period 4 and Group 4 of the periodic table (the first of the transition metals in this period).
Scandium (Sc) - Atomic number 21 , located in period 4 and is the first element in the transition series, Group 3 of the periodic table.
Zinc (Zn) - Atomic number 30 , located at the end of period 4 in the transition metals, specifically Group 12 of the periodic table. It has a completely filled d-subshell in its ground state.
Nickel (Ni) - Atomic number 28 , located in period 4 , and is in Group 10 of the periodic table.
Now, considering the trends in ionization energy across the periodic table:
Going from Sc to Zn (left to right) in the same period, generally, the ionization energy should increase because of the increased nuclear charge.
Scandium has a 3d14s2 configuration, so it would have lower ionization energy compared to Zinc, which has a 3d104s2 configuration, since Zinc's d-subshell is completely filled, adding to the stability and requiring more energy to remove an electron.
Nickel has the electron configuration 3d84s2, so it has higher ionization energy compared to Scandium as well, but less than Zinc since Zinc has a completely filled d-subshell configuration that contributes to stability.
Titanium with the electron configuration 3d24s2 would have higher ionization energy than Scandium as it is to the right of Scandium but lower than that of Zinc for the same reasons discussed above.
Hence, Zinc (Zn) has the highest ionization enthalpy among the given elements due to its filled dsubshell which makes it highly stable relative to the other elements listed.
The correct answer is Option C: Zn.
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