Which group of elements in the periodic table has the largest first ionization energy (Ei1), and which group has the smallest? Explain.

Verified step by step guidance

1. Step 1: Understand the concept of first ionization energy (Ei1), which is the energy required to remove the outermost electron from a neutral atom in the gaseous state.
2. Step 2: Recall the general trend of ionization energy across the periodic table: it increases across a period from left to right and decreases down a group.
3. Step 3: Identify the group with the largest first ionization energy. Elements in Group 18 (Noble Gases) have the largest Ei1 because they have a full valence shell, making it difficult to remove an electron.
4. Step 4: Identify the group with the smallest first ionization energy. Elements in Group 1 (Alkali Metals) have the smallest Ei1 because they have a single electron in their outermost shell, which is relatively easy to remove.
5. Step 5: Consider the atomic structure and electron configuration to understand why these trends occur, focusing on the effective nuclear charge and electron shielding effects.