In the composition of the Earth crust, which one of the following is the second most abundant metal present by mass, after aluminium?

Introduction / Context:
Questions on the abundance of elements and metals in the Earth crust are common in general science and geography sections of competitive exams. Many candidates know that aluminium is the most abundant metal in the crust, but they sometimes become confused about which metal comes next. This question specifically asks for the second most abundant metal by mass in the crust, testing your recall of standard crustal composition data.

Given Data / Assumptions:

• The focus is on metals, not all elements.
• The reference layer is the Earth crust, not the whole Earth or the atmosphere.
• Options are Iron, Aluminum, Copper, and Zinc.
• Standard average crustal composition is assumed from basic geology references.

Concept / Approach:
By mass, the most abundant metal in the Earth crust is aluminium, largely present in feldspars and other aluminosilicate minerals. The second most abundant metal is iron, which occurs in many silicate minerals and in various iron rich ores. While copper and zinc are economically important, they are classified as trace or minor metals in the crust and are much less abundant than aluminium and iron. Therefore, if aluminium is first among metals, iron must be second in abundance, which matches standard geological tables.

Step-by-Step Solution:
Step 1: Recall that aluminium is widely accepted as the most abundant metal in the Earth crust, present in minerals such as feldspars, micas, and bauxites. Step 2: Understand that the question asks for the second most abundant metal, so aluminium, even though important, cannot be the correct choice here. Step 3: Look at iron, which is present in many common minerals such as pyroxenes, amphiboles, biotite, magnetite, and hematite. Step 4: Compare this with copper and zinc, which occur in smaller amounts in specific ore deposits but are not widespread major components of ordinary crustal rocks. Step 5: Standard data show that after aluminium, iron is the metal with the next highest mass percentage in the crust. Step 6: Therefore, the correct answer is iron as the second most abundant metal in the Earth crust.

Verification / Alternative check:
If you examine typical tables of crustal composition, aluminium is listed as a major element with a high mass percentage, and iron follows closely as another major element. Copper and zinc appear in much smaller amounts, usually in the trace element category. Many exam oriented textbooks explicitly state that aluminium is the most abundant metal and iron is the second most abundant metal, which confirms the selection of iron as the correct answer.

Why Other Options Are Wrong:

• Aluminum: It is the most abundant metal, not the second most abundant, so it does not fit the specific wording of the question.
• Copper: Economically important but present only in small quantities and restricted ore bodies, far below iron in total crustal abundance.
• Zinc: Similar to copper, it appears in limited ore deposits and contributes only a tiny proportion of the crust mass.

Common Pitfalls:
A frequent error is to read the question quickly and answer aluminium, forgetting that the question asks for the second most abundant metal, not the first. Others may be influenced by economic significance and choose copper or zinc because they are mined heavily. To avoid such mistakes, focus on the word second and remember the simple pairing for exams: aluminium is the most abundant metal, and iron is the second most abundant metal in the Earth crust.

Final Answer:
The second most abundant metal in the Earth crust is Iron.