Answer
See explanation
Work Step by Step
The most abundant elements in Earth’s crust (by mass) are:
Oxygen (O) ~ 46%
Silicon (Si) ~ 28%
Others: Al, Fe, Ca, Na, K, Mg
It makes sense because rocks are mostly silicate minerals (compounds of Si and O), so O and Si dominate by mass.
The most abundant elements in oceans (by mass of dissolved elements, mainly water) are:
Oxygen (O) ~ 86% (from H₂O)
Hydrogen (H) ~ 11% (from H₂O)
Others: Cl, Na, Mg, Ca, K, S
It makes sense because water (H₂O) makes up most of the ocean’s mass, so O and H are the most abundant.
The most abundant elements in atmosphere (by mass) are:
Nitrogen (N₂) ~ 78% (by volume → mass slightly less due to N atomic mass)
Oxygen (O₂) ~ 21% (by volume)
Others: Argon, CO₂, trace gases
It makes sense because nitrogen is the most abundant gas in air; oxygen is next. The composition is what we breathe.
Most abundant elements in the human body (by mass)
Oxygen (O) ~ 65%
Carbon (C) ~ 18%
Hydrogen (H) ~ 10%
Nitrogen (N) ~ 3%
It makes sense as the body is mostly water (H₂O) and organic molecules (carbohydrates, lipids, proteins, nucleic acids).
Oxygen: in water and biomolecules
Carbon: backbone of organic molecules
Hydrogen: in water and organic molecules
Nitrogen: in proteins and nucleic acids
