Determining the most abundant element depends entirely on the location being analyzed, whether it is the vast emptiness of space, the dense structure of a planet, or the composition of a living organism. While one element holds the clear title for the entire cosmos, the winner changes significantly when the scope narrows to our own solar system and home world.
The Universal Winner
The undisputed champion for elemental abundance across the entire universe is hydrogen. This simplest element accounts for approximately 75% of the universe’s total elemental mass. Hydrogen was the first element to form, created just moments after the Big Bang during a process known as Big Bang nucleosynthesis.
The next most common element in the cosmos is helium, making up about 23% to 25% of the total elemental mass. Together, hydrogen and helium constitute over 98% of all ordinary matter in existence. All elements heavier than these two light gases were generated much later inside stars and during explosive stellar events.
Hydrogen serves as the primary fuel source for stars, including our Sun, powering them through nuclear fusion. In this process, four hydrogen nuclei combine under immense heat and pressure to form a single helium nucleus, releasing vast amounts of energy. This continuous stellar activity slowly converts the universe’s most common element into the second most common one.
Elemental Abundance on Earth
The composition of Earth presents a sharp contrast to the universal average. While the entire planet is predominantly composed of iron, this is largely due to the massive, dense core beneath the surface. Iron makes up roughly 32% of the planet’s total mass, followed by oxygen and silicon.
Analyzing the Earth’s crust, the thin outer shell we inhabit, provides a different perspective. In this layer, oxygen is the most abundant element, accounting for about 46.6% of the crust by mass. This prevalence stems from oxygen’s high reactivity, causing it to readily bond with other elements to form minerals.
Oxygen combines extensively with silicon, the second most abundant crustal element at approximately 27.7% of the mass. These two elements form the silicate minerals, which are the fundamental building blocks of most rocks and sands. The third and fourth most common elements in the crust are aluminum and iron, respectively.
The Building Blocks of the Human Body
The elemental makeup of the human body reveals another distinct pattern of abundance. Oxygen maintains its top position by mass, comprising about 65% of the body’s weight. This high percentage is primarily because the human body is mostly composed of water, where oxygen accounts for a significant portion of the water molecule’s mass.
The four elements that form the majority of biological matter are collectively known as the CHON elements: Carbon, Hydrogen, Oxygen, and Nitrogen. Carbon is the second most abundant element at approximately 18% of body mass. Its unique ability to form four stable bonds allows it to serve as the structural backbone for all organic molecules, including proteins and DNA.
Hydrogen, despite being the most numerous atom in the body, ranks third by mass at about 10%. Nitrogen, a fundamental component of amino acids and nucleic acids, accounts for approximately 3% of the body’s mass. These four elements combine to form nearly 96% of the mass of a human being.