Which element from Group 7A has lowest ionization energy.

• A. I
• B. Br
• C. Cl
• D. F
• E. Ne

Answer: (A)

Verified step by step guidance

1. Understand the concept of ionization energy: Ionization energy is the energy required to remove an electron from an atom in the gaseous state. It generally increases across a period and decreases down a group in the periodic table.
2. Identify the elements in Group 7A (also known as Group 17 or the halogens): The elements listed are Iodine (I), Bromine (Br), Chlorine (Cl), and Fluorine (F). Neon (Ne) is not a halogen; it is a noble gas from Group 8A.
3. Recall the trend in ionization energy within a group: As you move down a group in the periodic table, the ionization energy decreases. This is because the outer electrons are further from the nucleus and are shielded by more inner electron shells, making them easier to remove.
4. Apply the trend to the halogens: Among the halogens listed, Iodine (I) is the furthest down the group, meaning it has the lowest ionization energy compared to Bromine (Br), Chlorine (Cl), and Fluorine (F).
5. Conclude that Iodine (I) has the lowest ionization energy among the halogens listed, based on its position in the periodic table and the trend of decreasing ionization energy down a group.