Final answer:
A strong reducing agent loses electrons easily, making it a poor oxidizing agent, while a strong oxidizing agent like fluorine gains electrons well and typically cannot act as a reducing agent. Transition metals exhibit varied behaviors with some being strong reducing agents and others like platinum and gold resisting oxidation, showing exceptions to the rule.
Step-by-step explanation:
Whether a strong reducing agent must be a weak oxidising agent, and vice versa, relates to the inherent chemical properties of these substances. A strong reducing agent is characterized by its tendency to lose electrons easily, which in turn makes it a less likely candidate to gain electrons and act as an oxidizing agent.
Conversely, a strong oxidizing agent, like fluorine, is very good at gaining electrons and thus typically does not act as a reducing agent.
Fluorine, being the most powerful oxidizing agent known, reacts with a majority of elements, forming binary fluorides. It does not exhibit positive oxidation states, indicating its inability to reduce others, which further stresses the concept that strong oxidizers are poor reducers.
Transition metals show that the principles governing oxidizing and reducing behaviors are not absolute. These metals showcase a spectrum of chemical behaviors where some may act as strong reducing agents, while others like platinum and gold have high reduction potentials and resist oxidation.
This displays that not all chemicals strictly adhere to the strong oxidizer equals weak reducer rule.