Which of these metals is the least easily oxidized? Na Ag Fe Au Ca
The Correct Answer and Explanation is:
The metal that is least easily oxidized among Na, Ag, Fe, Au, and Ca is gold (Au).
To explain this, oxidation refers to the loss of electrons by a metal atom. A metal that is least easily oxidized is one that resists losing electrons and therefore has a higher tendency to remain in its metallic state. This behavior can be predicted by looking at the electrochemical series, which ranks metals based on their tendency to lose electrons (oxidize). The more positive the metal’s electrode potential, the less likely it is to oxidize.
Gold has a very high electrode potential, meaning it is quite stable and resistant to oxidation. It does not easily form positive ions because it has a strong attraction for its electrons. This is one reason why gold does not tarnish or rust over time, unlike many other metals.
In contrast, calcium (Ca) and sodium (Na) are highly reactive metals. Both of these metals are found in Group 1 and Group 2 of the periodic table, which makes them very prone to oxidation. Sodium, for example, reacts violently with water, losing electrons to form Na+ ions. Similarly, calcium, though less reactive than sodium, still reacts readily with water and oxidizes quickly in air.
Iron (Fe) is more easily oxidized than gold but less so than sodium or calcium. It forms iron oxide (rust) when exposed to moisture and oxygen.
Lastly, silver (Ag) is more resistant to oxidation than iron and calcium, but not as much as gold. It tarnishes over time, turning black due to the formation of silver sulfide (Ag2S) when exposed to sulfur compounds in the air.
Thus, gold is the least easily oxidized metal because of its high resistance to losing electrons, making it one of the most stable metals in natural conditions.
