Which element has the following ground-state electron configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$?

• A. Sodium (Na)
• B. Argon (Ar)
• C. Sulfur (S)
• D. Chlorine (Cl)

Answer: (D)

Verified step by step guidance

1. First, write out the given electron configuration clearly: \$1s^2 2s^2 2p^6 3s^2 3p^5$.
2. Next, count the total number of electrons by adding the superscripts: \$2 + 2 + 6 + 2 + 5$.
3. Sum these numbers to find the total number of electrons, which corresponds to the atomic number of the element.
4. Recall that the atomic number determines the element on the periodic table, so identify the element with this atomic number.
5. Finally, match the atomic number to the element name; this will give you the element with the given ground-state electron configuration.