Final answer:
In plants, sunlight energy excites electrons in chlorophyll molecules during photosynthesis, energizing them to higher levels which in turn facilitates the splitting of water, generating energy for sugar synthesis.
Step-by-step explanation:
Electrons in atoms of chlorophyll molecules in plants get "excited" by sun energy during the process of photosynthesis. When light energy from the sun strikes chlorophyll or an accessory pigment within a plant cell's chloroplast, it energizes electrons within the pigment molecules. As these electrons absorb energy, they are elevated to higher energy levels, making them 'excited.' The energy from the 'excited' electrons is used to split water (H2O) molecules, which releases additional electrons and hydrogen ions, both of which play critical roles in the formation of ATP and NADPH, providing the energy necessary for the synthesis of sugars and other organic molecules critical to plant growth and energy storage.