To determine which ion has a stable valence electron configuration, we need to look at the common charge for each of the elements and how they relate to achieving an octet (8 valence electrons), which is a stable electron configuration.
A. Magnesium (Mg) typically loses 2 electrons to achieve a stable configuration, resulting in a 2+ charge. A 1- charge would not provide a stable configuration for magnesium.
B. Potassium (K) typically loses 1 electron to achieve a stable configuration (1+ charge), resulting in a stable noble gas configuration similar to argon.
C. Fluorine (F) typically gains 1 electron to achieve a stable configuration (1- charge), resulting in a stable noble gas configuration similar to neon. A 1+ charge would not provide stability for fluorine.
D. Sulfur (S) typically gains 2 electrons to achieve a stable configuration (2- charge). A 1- charge doesn’t fully utilize the ability of sulfur to achieve the octet, as it would leave it with only 7 valence electrons.
Considering this, the only option that describes an ion with a stable valence electron configuration is:
B. Potassium (K) with a 1+ charge.
This results in potassium attaining a noble gas configuration, thus achieving stability.