Which of the following elements is the most metallic?

The correct choice is based on the understanding of metallic character within the periodic table. Metallic character typically increases as one moves down a group and decreases across a period from left to right. This trend is linked to the atomic structure: elements that are more metallic tend to have a lower electronegativity, can easily lose electrons, and have larger atomic radii due to fewer electrons being held by the nucleus.

Bismuth, with the symbol Bi, is located further down in group 15 of the periodic table. As a heavier element, it possesses more metallic characteristics than the other options presented. The elements listed—phosphorus (P), sulfur (S), and selenium (Se)—are either nonmetals or metalloids that do not exhibit as strong metallic properties. Bismuth is a post-transition metal and, thus, has properties such as conductivity and malleability that are characteristic of metals.

Therefore, bismuth stands out as the most metallic among the answer choices, reinforcing the general trend that lower and leftward elements within the periodic table tend to have greater metallic character.