Multiple choice

The most abundant elements in earth's crust are

  1. oxygen and iron

  2. silicon and magnesium

  3. silicon and aluminum

  4. oxygen and silicon
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Oxygen (46-47%) and silicon (27-28%) are the two most abundant elements in Earth's crust by mass. Oxygen is found in silicates, oxides, and water. Silicon is the second most abundant and is the foundation of silicate minerals that make up most rocks. Options A, B, and C are incorrect because while iron, magnesium, and aluminum are abundant, they rank below oxygen and silicon. Aluminum is actually the third most abundant (~8%), followed by iron (~5%) and calcium (~3.6%).

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