Understanding Atomic Number and Mass Number: A Simple Guide for Chemistry Beginners

Have you ever looked at the periodic table and wondered what those numbers really mean? If you’re a student studying chemistry or just curious about atoms, understanding the atomic number and mass number is key to unlocking the secrets of elements. In this post, I’ll guide you step-by-step on how to identify the atomic number, calculate the mass number, and find out how many neutrons are in an atom — using real examples from elements like lithium, beryllium, and sodium. What Is the Atomic Number? Let’s start with the basics: the atomic number. The atomic number of an element tells you the number of protons in the nucleus of its atoms. Protons are positively charged particles that, along with neutrons, make up the nucleus of an atom. The atomic number is usually the smaller number displayed on the periodic table square for each element. For example, magnesium has an atomic number of 12, which means every magnesium atom contains 12 protons in its nucleus. Boron, on the other han...