Final answer:
The ionization energy of elements generally increases from left to right across the periodic table. In aluminum, each successive ionization energy increases, with a particularly large increase in the 4th ionization. This is due to the decrease in atomic size and the increase in effective nuclear charge, which make it more difficult to remove an electron.
Step-by-step explanation:
The ionization energy of an element refers to the amount of energy required to remove an electron from an atom or ion in its gaseous state. As you move across a row on the periodic table from left to right, the ionization energies generally increase. This is due to the decrease in atomic size and the increase in effective nuclear charge. The valence electrons are attracted more strongly to the nucleus, making it more difficult to remove an electron and resulting in an increase in ionization energy.
In the case of aluminum, each successive ionization energy increases because it becomes increasingly difficult to remove an electron as more electrons are already missing. The 4th ionization of aluminum experiences a particularly large increase because it involves removing an electron from a filled core level, which requires a significantly higher amount of energy. This trend can be explained by the fact that the chemistry of the elements mainly involves their valence electrons and removing or sharing inner electrons requires too much energy.