2. based on electron configuration, which atoms has the greatest radius? ne3s²3p³ ne3s²3p⁴ ne3s²3p⁵ ar4s²…

Explanation:

Step1: Identify the elements

The electron - configurations represent:

• $[\text{Ne}]3s^{2}3p^{3}$ is phosphorus (P) with atomic number 15.
• $[\text{Ne}]3s^{2}3p^{4}$ is sulfur (S) with atomic number 16.
• $[\text{Ne}]3s^{2}3p^{5}$ is chlorine (Cl) with atomic number 17.
• $[\text{Ar}]4s^{2}$ is calcium (Ca) with atomic number 20.

Step2: Recall the trend of atomic radius

Atomic radius generally decreases across a period (from left - to - right) due to increasing nuclear charge that pulls the electrons closer to the nucleus. Atomic radius increases down a group (from top - to - bottom) because of the addition of new electron shells.

• P, S, and Cl are in the third period. Ca is in the fourth period.
• Since Ca is in a higher period (has an additional electron shell) compared to P, S, and Cl, it has the largest atomic radius.

Answer:

$[\text{Ar}]4s^{2}$