Atomic Radius Order F9F7B0

1. **Problem Statement:** Determine which list of elements is arranged from smallest to largest atomic radius. 2. **Concepts and Rules:** Atomic radius generally decreases across a period (left to right) in the periodic table and increases down a group (top to bottom). 3. **Analyze each list:** - List 1: $K, Ca, Sc$ - All are in period 4: $K$ (group 1), $Ca$ (group 2), $Sc$ (group 3). - Atomic radius decreases from left to right, so $K > Ca > Sc$. - Given order is $K, Ca, Sc$ which is from largest to smallest, not smallest to largest. - List 2: $K, Na, Li$ - All are in group 1: $Li$ (period 2), $Na$ (period 3), $K$ (period 4). - Atomic radius increases down the group, so $Li < Na < K$. - Given order is $K, Na, Li$ which is largest to smallest, not smallest to largest. - List 3: $F, Cl, Br$ - All are in group 17: $F$ (period 2), $Cl$ (period 3), $Br$ (period 4). - Atomic radius increases down the group, so $F < Cl < Br$. - Given order is $F, Cl, Br$ which is smallest to largest. - List 4: $Ge, P, O$ - All are in period 3 or 4: $O$ (period 2), $P$ (period 3), $Ge$ (period 4). - Across period 3, atomic radius decreases left to right, but $Ge$ is in period 4. - Order $Ge, P, O$ is not smallest to largest. 4. **Conclusion:** The list arranged from smallest to largest atomic radius is $F, Cl, Br$. **Final answer:** $F, Cl, Br$