Suppose G is an undirected simple graph. A topological index for G is a number with this property that it is invariant under all graph isomorphisms with applications in chemistry. The Sombor and reduced Sombor indices of G are defined as S O G   =   ∑ u v   ∈ E G d G 2 u + d G 2 v and S O red G = ∑ u v   ∈ E G d G u − 1 2 + d G v − 1 2   , respectively. Here, d G u denotes the degree of the vertex u in G . In this paper, these invariants were computed for alkanes, alkyls, and annulenes. A comparison of our calculations with molecular mass is also presented. As a consequence, it is shown that there is a good correlation between Sombor index and molecular mass of these compounds.