What is the metallic radius?

Part 1: Definition of metallic radius:

• It is half the distance between the nuclei of two metal atoms in a metallic structure.
• The atoms are joined by metallic bonds in this kind of metallic structure.

Part 2: Trend of metallic radius in the periodic table:

• On moving across a period from left to right, the metallic radius generally decreases due to an increase in the effective nuclear charge.
• On moving from top to bottom in a group, the metallic radius generally increases due to an increase in principal quantum number.