What two elements are different from all other elements this stand alone on the periodic table?

The two elements that stand out on the Periodic Table are hydrogen and helium. Hydrogen, with its atomic number 1, is unique as it is the lightest and most abundant element in the universe, often existing as a diatomic molecule (H₂) rather than as a single atom. Helium, with atomic number 2, is a noble gas and is notable for being inert and existing primarily as a monatomic gas (He) under standard conditions. Both elements occupy distinct positions in the periodic table, with hydrogen often placed at the top left and helium at the top right.