Chlorophyll molecule contains which of the following as a central metal ion?

Explanation

Chlorophyll is a pigment essential for photosynthesis, and its structure includes a magnesium (Mg2+) ion at the center of a porphyrin ring. This central magnesium ion plays a pivotal role in the absorption of light energy. The other metal ions listed, such as iron (Fe2+), zinc (Zn2+), and copper (Cu2+), serve different functions in plant physiology but are not part of the chlorophyll structure. Thus, option D, Mg2+, is the correct answer.