Which periodic trend measures the size of an atom from the nucleus to the outermost electron?

• A. Ionization energy
• B. Atomic radius
• C. Electron affinity
• D. Electronegativity

Answer: (B)

Verified step by step guidance

1. Understand that the question asks about a periodic trend that measures the size of an atom from the nucleus to the outermost electron.
2. Recall the definitions of the given periodic trends: Ionization energy is the energy required to remove an electron from an atom; Electron affinity is the energy change when an atom gains an electron; Electronegativity is the tendency of an atom to attract electrons in a chemical bond.
3. Recognize that the size of an atom is described by the Atomic radius, which is the distance from the nucleus to the outermost electron cloud.
4. Note that Atomic radius generally decreases across a period (left to right) due to increasing nuclear charge pulling electrons closer, and increases down a group due to the addition of electron shells.
5. Conclude that the periodic trend measuring atomic size is the Atomic radius.