Here's why:

* Physical Properties: Sodium is a soft, silvery-white, highly reactive solid at room temperature. These are characteristics of metals.

* Chemical Properties: Sodium readily loses an electron to form a positive ion, which is a hallmark of metals. This tendency to lose electrons and form cations makes sodium highly reactive.

* Location on the Periodic Table: Sodium is located in Group 1 of the periodic table, which is the alkali metal group, consisting entirely of metals.

Non-metals typically have the following characteristics:

* They are dull and brittle.

* They are poor conductors of heat and electricity.

* They tend to gain electrons to form negative ions.

Therefore, sodium exhibits all the characteristics of a metal and none of the characteristics of a non-metal.