The periodic table | Atoms, elements, and the periodic table | High school chemistry | Khan Academy

Courses on Khan Academy are always 100% free. Start practicing—and saving your progress—now! The periodic table organizes elements into groups and periods based on their chemical and physical properties. Elements in the same group share similar characteristics, like reactivity. The table is divided into metals, nonmetals, and metalloids, each with distinct properties. Key groups include alkali metals, alkaline earth metals, halogens, and noble gases. Khan Academy is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We offer quizzes, questions, instructional videos, and articles on a range of academic subjects, including math, biology, chemistry, physics, history, economics, finance, grammar, preschool learning, and more. We provide teachers with tools and…