Rank according to third ionization energy, from smallest to largest.Ca (Z = 20) , Zn (Z = 30) , Ga (Z = 31) , As (Z = 33)

To rank the elements according to their third ionization energy from smallest to largest, we need to consider their atomic numbers (Z).

The atomic numbers of the given elements are as follows: Ca (Z = 20) Zn (Z = 30) Ga (Z = 31) As (Z = 33)

The third ionization energy generally increases as we move across a period from left to right in the periodic table. This is because as we move across a period, the effective nuclear charge increases, making it more difficult to remove an electron.

Based on this trend, we can rank the elements as follows:

1. Ca (Z = 20) - The third ionization energy of calcium is expected to be the smallest among the given elements since it is located towards the left side of the periodic table.

2. Zn (Z = 30) - The third ionization energy of zinc is expected to be higher than that of calcium but lower than the remaining elements since it is located in the middle of the given elements.

3. Ga (Z = 31) - The third ionization energy of gallium is expected to be higher than that of zinc since it is located towards the right side of the periodic table.

4. As (Z = 33) - The third ionization energy of arsenic is expected to be the largest among the given elements since it is located towards the far right side of the periodic table.

Therefore, the ranking of the elements according to their third ionization energy from smallest to largest is: Ca < Zn < Ga < As.