Which element in the periodic table has the smallest ionization energy? Which element has the largest ionization energy?

Verified step by step guidance

1. Step 1: Understand the concept of ionization energy, which is the energy required to remove an electron from an atom in the gaseous state.
2. Step 2: Recall the periodic trend for ionization energy: it generally increases across a period (from left to right) and decreases down a group (from top to bottom) in the periodic table.
3. Step 3: Identify the element with the smallest ionization energy. This is typically found at the bottom of Group 1 (alkali metals), as these elements have the least attraction between the nucleus and the outermost electron.
4. Step 4: Identify the element with the largest ionization energy. This is typically found at the top of Group 18 (noble gases), as these elements have a full valence shell and a strong attraction between the nucleus and the outermost electrons.
5. Step 5: Consider exceptions and specific elements: While the general trend helps, specific elements like Helium (He) have the highest ionization energy due to their small size and full valence shell, and Francium (Fr) has the lowest due to its large size and single valence electron.