A student is asked to identify the strongest reducing agent among the following elements. Which element is the strongest reducing agent?
- AFluorine (F)
- BOxygen (O)
- CChlorine (Cl)
- DLithium (Li)
Show answer & explanationAnswer & explanation
Correct answer: D. Lithium (Li)
A reducing agent is a substance that readily donates electrons (is oxidized) to another substance. The stronger the reducing agent, the more easily it loses electrons. Reducing strength generally increases down a group and decreases across a period from left to right on the periodic table. Alkali metals (Group 1), like Lithium, are excellent reducing agents because they have a strong tendency to lose their single valence electron. Halogens (F, Cl) and Oxygen are strong oxidizing agents, meaning they readily gain electrons.
Why the other options are wrong
- A. Fluorine is the strongest oxidizing agent, meaning it readily gains electrons, so it is a very poor reducing agent.
- B. Oxygen is a strong oxidizing agent, meaning it readily gains electrons, so it is a poor reducing agent.
- C. Chlorine is a strong oxidizing agent, though less so than fluorine, and is a poor reducing agent.
Reducing Agent Strength
A reducing agent is a chemical species that donates electrons to another species in a redox reaction. The strength of a reducing agent is inversely related to its ionization energy and directly related to its tendency to be oxidized.
- Strong reducing agents readily lose electrons.
- Alkali metals (Group 1) are strong reducing agents.
- Reducing strength increases down a group.
- Reducing strength decreases across a period (left to right).
Memory trick: Left & Down = Reducing; Right & Up = Oxidizing.