Question

a piece of sodium metal can be described as
o a pure substance and a compound.
o an impure substance that is reactive.
o an impure substance that is unreactive.
o a pure substance and an element.

Explanation:

A pure substance is either an element or a compound. Sodium metal (\(Na\)) is made up of only sodium atoms. An element is a pure substance that cannot be broken down into simpler substances by chemical means. Sodium is an element as it consists of only one type of atom (\(Na\) atoms). A compound is a pure substance formed by the chemical combination of two or more different elements. Since sodium is only one element, it is not a compound. An impure substance is a mixture. Sodium metal is not a mixture. Sodium is a highly reactive metal (for example, it reacts vigorously with water, \(2Na + 2H_2O=2NaOH + H_2\uparrow\)). But the key point here is about the classification as a pure - substance and an element.

Answer:

a pure substance and an element.