The first two elements in the periodic table are hydrogen (H) and helium (He). Hydrogen, with the atomic number 1, is the lightest and most abundant element in the universe, primarily found in stars and gas giants. Helium follows as the second element with an atomic number of 2; it is a noble gas known for its low reactivity and is commonly used in balloons and cryogenics. These two elements play critical roles in various scientific fields, including chemistry, astronomy, and physics, forming the foundation for understanding more complex atomic structures and interactions.