What is always true of a binary compound?

Answer;

It has two elements

Explanation;Binary compounds are substances that are made up of exactly two elements. An element is a substances that can not be broken down into smaller particles by chemical means. A binary compound is composed of two different elements, such that there may be only one of each element, for example sodium chloride (NaCl), it has one sodium and one chloride.  Other binary compounds will have more than one of each element, for example, nitrous oxide (N2O), which has two nitrogen and one oxygen.