Which statement best describes a compound?

A compound is best described as a chemically unique combination of two or more elements. This definition highlights that a compound is formed through chemical bonds, where the constituent elements lose their individual properties and create a new substance with distinct characteristics. This unique arrangement and bonding lead to properties that are different from those of the original elements.

For instance, water (H2O) is a compound formed from the elements hydrogen and oxygen. In this relationship, hydrogen and oxygen undergo a chemical change that results in water, which exhibits properties that neither hydrogen nor oxygen possesses in their elemental forms.

The other choices do not accurately capture the definition of a compound. A mixture of elements does not involve chemical bonding and retains the individual properties of its components. A solution, while describing a homogeneous mixture where one substance dissolves in another, is not specific to compounds alone. Lastly, a collection of elements in their natural state might refer to an element's form but does not imply any chemical combination, which is essential to define a compound.