Percent Composition

Water is 88.9% oxygen by mass - hydrogen is light despite being 2 atoms

Table salt is 60.7% chlorine, 39.3% sodium - chlorine dominates by mass

Sugar (C12H22O11) is 42% carbon, 6.5% hydrogen, 51.5% oxygen

Diamonds are 100% carbon - the only gemstone made of a single element

Bones are about 70% calcium phosphate (Ca3(PO4)2) by dry weight

Chlorophyll is only 2.7% magnesium, but that atom is essential for photosynthesis

Lithium-ion batteries contain only 2-7% lithium by weight

Hemoglobin is 0.34% iron - tiny amount but critical for oxygen transport