MCAT General Chemistry Review - Alexander Stone Macnow, MD 2019-2020

Atomic Structure

Chapter Profile


The content in this chapter should be relevant to about 6% of all questions about general chemistry on the MCAT.

This chapter covers material from the following AAMC content category:

4E: Atoms, nuclear decay, electronic structure, and atomic chemical behavior


Chemistry is the investigation of the atoms and molecules that make up our bodies, our possessions, the food we eat, and the world around us. There are different branches of chemistry, three of which are tested directly on the MCAT: general (inorganic) chemistry, organic chemistry, and biochemistry. Ultimately, all investigations in chemistry are seeking to answer the questions that confront us in the form—the shape, structure, mode, and essence—of the physical world that surrounds us.

Many students feel similarly about general chemistry and physics: But I’m premed, they say. Why do I need to know any of this? What good will this be when I’m a doctor? Do I only need to know this for the MCAT? Recognize that to be an effective doctor, one must understand the physical building blocks that make up the human body. Pharmacologic treatment is based on chemistry; many diagnostic tests used every day detect changes in the chemistry of the body.

So, let’s get down to the business of learning and remembering the principles of the physical world that help us understand what all this “stuff ” is, how it works, and why it behaves the way it does—at both the molecular and macroscopic levels. In the process of reading through these chapters and applying your knowledge to practice questions, you’ll prepare yourself for success not only on the Chemical and Physical Foundations of Biological Systems section of the MCAT but also in your future career as a physician.

This first chapter starts our review of general chemistry with a consideration of the fundamental unit of matter—the atom. First, we focus on the subatomic particles that make it up: protons, neutrons, and electrons. We will also review the Bohr and quantum mechanical models of the atom, with a particular focus on the similarities and differences between them.

MCAT Expertise

The building blocks of the atom are also the building blocks of knowledge for the general chemistry concepts tested on the MCAT. By understanding these particles, we will be able to use that knowledge as the “nucleus” of understanding for all of general chemistry.