Q.₁₃Al is a metal, ₁₄Si is a metalloid and ₁₅P is a nonmetal.

Step 1. Locate the zig-zag dividing line. Section 7.4.2/7.5.3.2 places metals to the left of a zig-zag line running through the p-block, nonmetals to its right, and metalloids along the line itself.

Step 2. Place each element in period 3. Al (group 13, 3 valence electrons) sits toward the metallic left side; Si (group 14, 4 valence electrons) sits directly on the dividing line; P (group 15, 5 valence electrons, higher electronegativity than Al or Si) sits on the nonmetallic right side. …

Locating three period-3 elements relative to the metal/metalloid/nonmetal …

• Assuming metallic/nonmetallic character is decided only by group number and ignoring the specific zig-zag-line position that defines metalloids. …