1. **Problem Statement:** We are given atomic radii of several elements and the information that atomic radius decreases from left to right across a period in the periodic table. 2. **Given Atomic Radii:** - Iodine (I): $11.5 \times 10^{-11}$ m - Tin (Sn): $4.5 \times 10^{-12}$ m - Antimony (Sb): $133.0 \times 10^{-13}$ m - Tellurium (Te): $0.123 \times 10^{-9}$ m - Another radius given: $1.45 \times 10^{-12}$ m (element not specified) 3. **Understanding Atomic Radius Trend:** - Atomic radius generally decreases from left to right across a period because the number of protons increases, pulling electrons closer. - This trend is shown by the arrow pointing from right to left indicating decreasing radius. 4. **Convert all radii to a common unit for comparison:** - $11.5 \times 10^{-11}$ m = $1.15 \times 10^{-10}$ m - $4.5 \times 10^{-12}$ m = $4.5 \times 10^{-12}$ m - $133.0 \times 10^{-13}$ m = $1.33 \times 10^{-11}$ m - $0.123 \times 10^{-9}$ m = $1.23 \times 10^{-10}$ m - $1.45 \times 10^{-12}$ m = $1.45 \times 10^{-12}$ m 5. **Order the radii from largest to smallest:** - Tellurium (Te): $1.23 \times 10^{-10}$ m - Iodine (I): $1.15 \times 10^{-10}$ m - Antimony (Sb): $1.33 \times 10^{-11}$ m - Tin (Sn): $4.5 \times 10^{-12}$ m - Unknown element: $1.45 \times 10^{-12}$ m 6. **Conclusion:** The atomic radius decreases from left to right in the periodic table row, consistent with the given data and the arrow direction. This confirms the periodic trend of atomic radius decreasing across a period from left to right.