Atomic Structure Basics
Atoms are the tiny particles that make up all matter in our universe. Each atom contains three main subatomic particles: protons (positively charged), neutrons (neutral), and electrons (negatively charged). The modern model of an atom divides it into two main regions: the nucleus and the electron cloud.
The nucleus sits at the center and contains both protons and neutrons, while electrons orbit around it in the electron cloud. Almost all of an atom's mass comes from its nucleus because protons and neutrons each have a mass of 1 atomic mass unit (amu), while electrons are incredibly light (only 1/2000 amu).
To identify atoms, we use the atomic number which tells us how many protons are in the nucleus. In a neutral atom, the number of electrons equals the number of protons. To find neutrons, simply subtract the atomic number from the atomic mass.
Quick Tip: The atomic number is your best friend for identifying elements! It tells you the number of protons, which never changes for a given element. No matter what form an element takes, its atomic number stays the same.
