Final answer:
The chemical symbol "Na" stands for the element sodium, while "NA" typically stands for non-applicable or not available, and does not represent a compound or element in chemistry.
Step-by-step explanation:
The difference between "Na" and "NA" lies in their nature as chemical substances. "Na" is the chemical symbol for sodium, which is an element listed on the periodic table. In contrast, "NA" does not represent a known chemical substance and is often used as an abbreviation for non-applicable or not available. However, if by "NA" we mean "Na" written incorrectly, then the answer would be that "Na" is an element, while "NA" suggests a typo or an undefined term in chemistry.
Elements are pure chemical substances consisting of a single type of atom, whereas compounds are substances formed when two or more elements combine in a fixed ratio. An example of a compound is sodium chloride (NaCl), which is an ionic compound made up of sodium and chlorine in a 1:1 ratio.