A large class of molecules is called a macromolecule.
 
        
             
        
        
        
Covalent Bonds: A Hydrogen Example. A covalent bond is a chemical bond that comes from the sharing of one or more electron pairs between two atoms. Hydrogen is an example of an extremely simple covalent compound. A hydrogen example.
        
             
        
        
        
There is a chance of change in colour in urine
        
             
        
        
        
Both are hard structures that reduce erosion causes by waves.