According to the electron configuration, which of the following elements has a completely filled 3p subshell?

• A. Ar (argon)
• B. Cl (chlorine)
• C. Na (sodium)
• D. P (phosphorus)

Answer: (A)

Verified step by step guidance

1. Recall that the 3p subshell can hold a maximum of 6 electrons because it has three p orbitals, each capable of holding 2 electrons.
2. Write the electron configurations for each element up to the 3p subshell:
3. - Sodium (Na): 1s\^2 2s\^2 2p\^6 3s\^1 (3p subshell is empty)
4. - Phosphorus (P): 1s\^2 2s\^2 2p\^6 3s\^2 3p\^3 (3p subshell is half-filled with 3 electrons)
5. - Chlorine (Cl): 1s\^2 2s\^2 2p\^6 3s\^2 3p\^5 (3p subshell has 5 electrons, not full)
6. - Argon (Ar): 1s\^2 2s\^2 2p\^6 3s\^2 3p\^6 (3p subshell is completely filled with 6 electrons)
7. Identify which element has the 3p subshell fully occupied by 6 electrons, which corresponds to a completely filled 3p subshell.