Here's why:

* Electrochemical Series: This series lists metals (and some non-metals) in order of their standard electrode potentials.

* Standard Electrode Potential: This value represents the tendency of a material to lose electrons and form positive ions. The more negative the value, the greater the tendency to lose electrons.

* Lithium's Position: Lithium sits at the very top of the electrochemical series with a very negative standard electrode potential. This means it has the highest tendency to lose electrons and become positively charged.

Important Note: The electrochemical series is a valuable tool for predicting the direction of redox reactions. However, the actual potential of a material can be influenced by factors like concentration, temperature, and the presence of other ions.