Basic Atomic Structure and Atomic Theory - Study Guide Atoms are one of the first topics covered in a chemistry course because they are the fundamental building block of matter. Atoms bond to each other to form pure elements, compounds, and alloys. These substances exchange atoms with each other to form new products through chemical reactions. Key Takeaways: Atoms Atoms are the smallest unit of matter that cannot be divided using any chemical method. They do consist of smaller parts, but can only be broken by nuclear reactions.The three parts of an atom are protons, neutrons, and electrons. Protons carry a positive electrical charge. Neutrons are electrically neutral. Electrons carry a negative charge, equal in magnitude to that of a proton.Protons and neutrons stick together to form the atomic nucleus. Electrons orbit around the nucleus.Chemical bonding and chemical reactions occur due to the electrons around atoms. An atom with too many or too few electrons is unstable and may bond with another atom to either share or essentially donate electrons.
