Elements-compounds-and-mixture-for-high-school-worksheet-3.docx When two or more chemical elements combined together in a fixed ratio that is called chemical compound. Element is a species of atom which is determined by the number of protons in the nuclei of its atoms. A B C D E C 1. Pure Element - only one type of atom present. E 2. Mixture of two elements - two types of uncombined atoms present. B 3.