<span>The answers are the substances found in the
simple compounds of Hydrogen</span><span>, ammonia, methane and water and when they will undergo melting or boiling, there are weak
'intermolecular forces' that break them which is the reason why it is not a strong
covalent bond.</span>
<em><u>The two substances that do not contain molecules with covalent bonds are ionic substances and single atoms.</u></em>
<em><u>Ionic substances are those substances that are formed as a result of transfer of electrons from one atom to another, resulting to formation of ions or stable ions. </u></em>Examples of such ions are sodium chloride, potassium iodide, etc. These compounds do not have molecules with covalent bonds.
<em><u>Single atoms on the other hand do not have molecules with covalent bond since they exist as an atom and not as a molecule.</u></em> They include elements such as magnesium, sodium,potassium, etc.