* Group 1 vs. Group 2: Sodium and lithium are both in Group 1 (alkali metals), while magnesium is in Group 2 (alkaline earth metals). Elements within the same group share similar chemical properties.

* Electron Configuration: Sodium and lithium have a single valence electron, which they readily lose to form a +1 ion. Magnesium, with two valence electrons, forms a +2 ion. This difference in electron configuration leads to variations in reactivity and bonding behavior.

* Reactivity: Sodium and lithium are highly reactive metals, reacting vigorously with water. Magnesium is less reactive, though it still reacts with water, albeit slower.

* Melting and Boiling Points: Sodium and lithium have relatively low melting and boiling points compared to magnesium. This is due to the weaker metallic bonding in Group 1 metals.

* Density: Sodium and lithium are both less dense than magnesium.

In summary, sodium shares more similarities with lithium in terms of reactivity, electron configuration, and physical properties due to their shared position as alkali metals.