Which of elements would you expect to form the following with copper? Substitutional solid solution with complete solubility Substitutional solid solution with incomplete solubility Interstitial solid solution.

Element Atomic Radius (nm) Crystal Structure Electronegativity Valence

Cu 0.1278 FCC 1.9 + 2

C 0.071

H 0.046

O 0.060

Ag 0.1445 FCC 1.9 + 1

Al 0.1431 FCC 1.5 + 3

Co 0.1253 HCP 1.8 + 2

Cr 0.1249 BCC 1.6 + 3

Fe 0.1241 BCC 1.8 + 2

Ni 0.1246 FCC 1.8 + 2

Pd 0.1376 FCC 2.2 + 2

Pt 0.1387 FCC 2.2 + 2

Zn 0.1332 HCP 1.6 + 2

The answers to the question are

(a) Copper will form substitutional solid solution with complete solubility with

Ni due to their very similar size, equal valency and similar electronegativities as well as Pd, and Pt but less likely with aluminium due to size and valency difference

(b) Copper will form substitutional solid solution of incomplete solubility with Ag, Al, Co, Cr, Fe, Zn

(c) Copper will form interstitial solid solution with

C, H, O due to the large difference between the size of copper atomic radius and the smaller atomic radii of C, H and O

Explanation:

Substitutional solid solution rules

the following are the Hume-Rothery rules for substitutional solid solutions:

1. Less than 15%difference between the atomic radius of the solute and solvent:

2. Similarity in the crystal structures of solute and solvent;

3. The valency of the solvent and solute must be similar before they can be said to be completely soluble in each other.

A lower valency metal is more likely to dissolve in one higher valency.

4. The electronegativities of the solute and solvent should be similar a wide variation in electronegativity will lead to the formation of intermetallic compounds rather than a solid solutions.