Which element is placed at the top of the electrochemical series?

1. Analyze the question

The question asks for the element positioned at the very top of the electrochemical series. In chemistry, the electrochemical series (or activity series) ranks elements based on their standard electrode potentials, specifically their tendency to lose electrons (oxidation) or gain electrons (reduction).

2. Explain the concept

The electrochemical series is a list of elements arranged in order of their standard electrode potentials ($E^0$).

• Top of the series: Elements at the top are the strongest reducing agents. They have the most negative standard electrode potentials, meaning they lose electrons very easily and are highly reactive. These are typically the alkali and alkaline earth metals (e.g., Potassium, Sodium, Calcium).
• Bottom of the series: Elements at the bottom are the strongest oxidizing agents. They have the most positive standard electrode potentials, meaning they hold onto their electrons tightly and are less reactive (e.g., Gold, Silver, Copper).
• Hydrogen: Hydrogen is used as the reference point in the series with a standard electrode potential of $0.00\text{ V}$.

3. Show the solution

Let's evaluate the options provided based on their positions in the electrochemical series:

• Copper (Cu): Located below Hydrogen. It is a poor reducing agent.
• Hydrogen (H): Located in the middle of the series (the reference point).
• Sodium (Na): Located very high up in the series. It is a highly reactive metal that loses electrons readily to form $\text{Na}^+$.
• Oxygen (O): While involved in redox reactions, it is generally not categorized as a metal in the standard electrochemical series of metals.

Comparing the options, Sodium is the most reactive metal listed and occupies a position significantly higher than Hydrogen and Copper. While Potassium and Lithium are actually at the very top of the full series, among the choices provided, Sodium is the correct representative of the highly reactive metals at the top.

4. Identify the answer

The correct option is C.

5. Tip

To remember the order of the most common metals in the electrochemical series, use this mnemonic: Please Stop Calling Me A Careless Zebra Instead Learn How Copper Saves Gold.

• Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Lead, Hydrogen, Copper, Silver, Gold.