Final answer:
The order of decreasing ionization energy for Aluminum (Al), Chlorine (Cl), Magnesium (Mg), and Sulfur (S) in the periodic table is Chlorine, Sulfur, Magnesium, and Aluminum due to their respective positions in the periodic trends.
Step-by-step explanation:
To place the elements Aluminum (Al), Chlorine (Cl), Magnesium (Mg), and Sulfur (S) in order of decreasing ionization energy, we need to consider their positions in the periodic table and the trends that affect ionization energy. Ionization energy generally increases across a period (from left to right) and decreases down a group (from top to bottom).
Given these trends, the order of decreasing ionization energy for the elements in question is:
- Chlorine (Cl)
- Sulfur (S)
- Magnesium (Mg)
- Aluminum (Al)
Chlorine, being furthest to the right and top among the listed elements, has the highest ionization energy. As we move to sulfur, ionization energy decreases slightly. Magnesium has a lower ionization energy than sulfur as it is to the left in the same period. Aluminum has the lowest ionization energy among them, as it sits below magnesium and to the left of sulfur and chlorine.