Question

Which of these statements best describes the relationship between elements, compounds, and pure substances?

Pure substances can be divided into two groups: elements and compounds.


Compounds can be divided into two groups: pure substances and elements.


Elements and pure substances are two of many different types of compounds.


Pure substances and compounds are two of many different types of elements.

Answer 1

pure substances can be divided into two groups; elements and compounds

Answer 2

Pure substances can be divided into two groups: elements and compounds.

Step-by-step explanation:

Pure substances can be recognized because they have a definite constant composition, as can be seen in the formula, and distinct chemical properties.

For example, H₂O is a pure substance where the relation of 2 atoms of Hydrogen to 1 atom of Oxygen is always true. O₂ is also a pure substance because 1 molecule of O₂ always contains two atoms of Oxygen.

As we can see from above, pure substances can be formed by one or more types of atoms. Substances formed by 2 or more types of atoms are known as compounds (e.g. H₂O, CO₂). Substances formed by 1 type of atoms are known as elements (e.g. Na, O₂, O₃).

Compounds and elements are kinds of pure substances, so they inherit all properties from them (definite constant composition, distinct chemical properties).