Final answer:
The correct order for decreasing IE1 (largest to smallest) is Element C, Element B, Element A.
Step-by-step explanation:
The correct order for decreasing IE1 (largest to smallest) is Element C, Element B, Element A.
The first ionization energy generally increases across a period and decreases down a group on the periodic table. However, there are exceptions to this trend, such as in the case of Element C (Sulfur), where the repulsion between electrons in the same p orbital makes it easier to remove an electron. Element B (Nitrogen) has a higher ionization energy than Element A (Lithium) because it has a higher atomic number and therefore more protons, leading to a stronger attraction between the nucleus and the outermost electron.