The "Atoms-First" approach has received considerable attention in the chemical education community over the past few years as an alternative to the standard reaction-based two-semester General Chemistry curriculum. The Atoms-First model emphasizes the electronic structure of the atom as a means to explain and rationalize chemical reactions and stoichiometry, which are then covered at the end of the first semester. The current study analyzes the results of switching from a traditional reaction-based curriculum to an Atoms-First approach in a two-semester General Chemistry course with regards to student performance on standardized American Chemical Society (ACS) exams. The study evaluated roughly 600 students over three years of classes, and found that the outcomes were generally favorable for topics related to atomic and molecular structure. A comparison of the two approaches and suggestions for implementation of the Atoms-First approach are also included.