Saturated hydrocarbons consists of C-C single bond whereas Unsaturated hydrocarbons consists C-C double/triple bond.
Pure substances are substances which are homogenous in nature. They either consists of atoms of 1 kind or molecules of 1 kind. Atoms are seen in elements, where as molecules are seen in compounds like Acids, Bases, etc.
They mostly have fixed properties like boiling and melting points and are uniform in nature. :D
Cu⇒ 1 atom
N⇒2 atoms
O⇒6 atoms
Total 9 atoms
<h3>Further explanation </h3>
The empirical formula is the smallest comparison of atoms of compound forming elements.
A molecular formula is a formula that shows the number of atomic elements that make up a compound.
<em>(empirical formula) n = molecular formula </em>
Chemical formula : Cu(NO₃)₂
Number of Cu : 1
Number of N : 2
Number of O = 2 x 3 = 6
Total atoms in Cu(NO₃)₂ : 1 + 2 + 6 = 9
The answer to this question is C: the ability to memorize
Hope this helps :)