What is the most abundant compound found on Earth?

Water is the most abundant compound found on Earth, primarily because it is present in vast quantities in the oceans, lakes, rivers, and even in the atmosphere as vapor. Covering approximately 71% of the Earth's surface, water plays a crucial role in sustaining life and regulating the planet's climate. It exists in three states: solid (ice), liquid (water), and gas (vapor), showcasing its versatility and importance in various natural processes.

While oxygen is indeed abundant in the atmosphere and essential for life, it primarily exists in its diatomic form (O2) and is not a compound by definition. Carbon dioxide, although significant in biological and ecological contexts, constitutes a much smaller part of the Earth's atmosphere in comparison to water. Salt, while abundant in ocean water in the form of sodium chloride, does not match the sheer volume and versatility of water across the Earth's environments. Thus, the overwhelming presence and fundamental role of water establish it as the most abundant compound on our planet.