Dear student, Reducing agents are those compounds which can reduce others compounds and get oxidize themselves. Alkali Metals act as strong reducing agents because alkali metals have only one valence electron in their valence shell. Therefore, It is easier for them to lose one electron and attain nearest noble gas configuration and become more stable than they were earlier.Thus they lose one electron and get oxidize themselves, reducing the other compound. This makes them strong reducing agent. Regards,