Which element has the smallest atomic radius?

Step 1: Define the Problem

Identify the element with the smallest atomic radius.

Step 2: Break Down the Problem

1. Understand the concept of atomic radius.
2. Determine which elements generally have smaller atomic radii.

Step 3: Apply Relevant Concepts

• Atomic radius generally decreases across a period from left to right in the periodic table due to increasing nuclear charge, which pulls electrons closer to the nucleus.
• Atomic radius generally increases down a group due to the addition of electron shells.

Step 4: Analysis, Verify and Summarize

• The smallest atomic radius is typically found among the noble gases at the end of a period.
• Helium (He), being at the top of the noble gases and having only one electron shell, has the smallest atomic radius.

Final Answer

Helium (He) has the smallest atomic radius.