Alkanes

To solve the problem, we need to identify the alkali metal with the lowest and highest standard electrode potential ( ).

1. Understanding Standard Electrode Potential ( ):
Standard electrode potential indicates how easily an element gets reduced (gains electrons). A more negative value means the metal is a better reducing agent and prefers to remain in the oxidized form (as a cation).

2. Electrode Potentials of Alkali Metals:

• Lithium (Li): (most negative)
• Sodium (Na):
• Potassium (K):
• Rubidium (Rb):
• Cesium (Cs):

So: - Lowest : Lithium (Li) - Highest : Sodium (Na)

3. Final Identification:
X = Li (lowest )
Y = Na (highest )

Final Answer:
The correct pair is Li, Na.