Question

for each list, place elements in order of least to greatest atomic radius: 1) ar argon na sodium si silicon 2) in indium ga gallium b boron 3) ne neon br bromine cs cesium

Explanation:

Step1: Recall atomic - radius trends

Atomic radius decreases across a period (left - to - right) and increases down a group (top - to - bottom) in the periodic table.

Step2: Analyze the first set (Ar, Na, Si)

Na, Si, and Ar are in the same period (Period 3). Na is on the left - most, Si is in the middle, and Ar is on the right - most. So, the order is Ar < Si < Na.

Step3: Analyze the second set (In, Ga, B)

B is in Period 2, Ga is in Period 4, and In is in Period 5. Since atomic radius increases down a group, the order is B < Ga < In.

Step4: Analyze the third set (Ne, Br, Cs)

Ne is in Period 2, Br is in Period 4, and Cs is in Period 6. So, the order is Ne < Br < Cs.

Answer:

1. Ar, Si, Na
2. B, Ga, In
3. Ne, Br, Cs