Crystal structure identification — FCC metals State whether the following is correct: “Face-centred cubic (FCC) lattice is found in gamma-iron, aluminium, copper, lead, silver, and nickel.”

Introduction / Context:
Recognising crystal structures of common metals is a foundation for understanding mechanical properties, slip systems, and phase transformations. FCC metals typically exhibit good ductility because of many operative slip systems.

Given Data / Assumptions:

• Room-temperature structures unless specified otherwise.
• Gamma-iron (austenite) refers to the high-temperature allotropic form of iron.

Concept / Approach:
Aluminium, copper, lead, silver, and nickel are classic FCC metals at room temperature. Iron is allotropic: alpha-iron (ferrite) is BCC at room temperature, gamma-iron (austenite) is FCC between about 910°C and 1400°C, and delta-iron is BCC again close to the melting point. The statement lists the FCC set correctly including the austenitic phase of iron.

Step-by-Step Solution:
Identify each metal’s structure: Al, Cu, Pb, Ag, Ni → FCC at room temperature.Recall that gamma-iron (not alpha) is FCC at high temperature.Therefore, the overall statement is true.

Verification / Alternative check:
Materials handbooks list these metals as FCC; phase diagrams confirm gamma-iron is the FCC allotropic form.

Why Other Options Are Wrong:

• False: contradicts well-established crystallography.
• Partial truths (option c) omit other FCC metals listed.
• “Gamma-iron is BCC”: incorrect; alpha-iron is BCC at room temperature.

Common Pitfalls:
Confusing alpha-iron (BCC) with gamma-iron (FCC) and overlooking allotropic changes with temperature in iron.

Final Answer:
True