Which of the following pairs of elements are found in the core of the Earth?

Step 1: Analyze the question The question asks which two elements make up the Earth's core.

Step 2: The concept The Earth has three main layers:

• Crust: the outer layer, rich in silicon and aluminium (sial) and silicon and magnesium (sima).
• Mantle: the middle layer, rich in silicates of iron and magnesium.
• Core: the innermost layer, made mostly of iron and nickel. It has two parts, a liquid outer core and a solid inner core.

The core is sometimes called NIFE, from Ni (nickel) and Fe (iron, from the Latin ferrum).

Step 3: Check the options

• A. Iron and Silicon: silicon is mainly in the crust and mantle, so this is wrong.
• B. Iron and Nickel: this matches the NIFE composition of the core, so it is correct.
• C. Iron and Calcium: calcium is found in the crust, in rocks like limestone, so this is wrong.
• D. Iron and Magnesium: magnesium is mostly in the mantle, so this is wrong.

Step 4: Answer The correct answer is B. Iron and Nickel.

Exam tip: Remember NIFE for the core. Think of the core as "Nickel + Iron (Fe)". Also remember SIAL (silica and aluminium) for the continental crust and SIMA (silica and magnesium) for the oceanic crust.