Which element is the most abundant in Earth's entire composition?

Which element is the most abundant in Earth's entire composition?

• A. Oxygen
• B. Iron
• C. Silicon
• D. Magnesium

Answer: (B)

The key idea is that the Earth’s mass is dominated by its metallic core. During the planet’s formation, heavy elements like iron and nickel sank to the center, forming a large iron-rich core. That core contains roughly a third of Earth’s total mass, so iron ends up being the most abundant element overall. In the crust, the most common element is actually oxygen (tied to silicon and other elements), and the mantle has a lot of magnesium, silicon, and oxygen, but those together do not contribute as much mass as the core does. So, when you look at the entire planet, iron’s prominent presence in the core makes it the most abundant element overall.

The key idea is that the Earth’s mass is dominated by its metallic core. During the planet’s formation, heavy elements like iron and nickel sank to the center, forming a large iron-rich core. That core contains roughly a third of Earth’s total mass, so iron ends up being the most abundant element overall.

In the crust, the most common element is actually oxygen (tied to silicon and other elements), and the mantle has a lot of magnesium, silicon, and oxygen, but those together do not contribute as much mass as the core does. So, when you look at the entire planet, iron’s prominent presence in the core makes it the most abundant element overall.