* Fixed Composition: A compound has a fixed and definite ratio of elements. In silicon dioxide, the ratio of silicon atoms to oxygen atoms is always 1:2.

* Chemical Bonding: The silicon and oxygen atoms are held together by strong chemical bonds (covalent bonds). This means they have formed a new substance with unique properties distinct from the individual elements.

* Distinct Properties: Silicon dioxide (quartz) has unique properties like hardness, high melting point, and electrical insulation that are different from the properties of silicon and oxygen alone.

Homogeneous mixtures, on the other hand, have variable compositions and their components retain their individual properties. For example, saltwater is a homogeneous mixture because the salt and water are not chemically bonded and can be separated.