3. How can millions of
compounds be made from the
atoms of about 100 elements?

The answer is that compounds are formed when elements are joined and held together by strong forces called chemical bonds. ... Covalent bonds share electrons between atoms in order to fill their electron shells. In the compound, molecules are held together by the attraction between the nucleus and the shared electrons.

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.