Question

instructions: rank the following atoms in order of increasing atomic radius.

1. ______ ar, br, ca, k
2. ______ ga, in, b, tl
3. ______ cl, i, br, f
4. ______ n, b, li, o

Explanation:

Step1: Recall atomic radius trends

Atomic radius decreases across a period (from left to right) and increases down a group.

Step2: Analyze each set

Set 1: \(Ar, Br, Ca, K\)

• \(Ar\) is a noble gas. \(Br\) is in group 17, \(Ca\) in group 2 and \(K\) in group 1.
• Across period 4: \(K\) (group 1) has larger radius than \(Ca\) (group 2) which has larger radius than \(Br\) (group 17). \(Ar\) (noble gas) has a slightly larger radius than halogens due to van - der - Waals radius measurement. But comparing metallic and non - metallic radii (using covalent radius for \(Br\), metallic for \(K\) and \(Ca\)): \(Br

Set 2: \(Ga, In, B, Tl\)

• \(B\) is in period 2, \(Ga\) in period 4, \(In\) in period 5 and \(Tl\) in period 6.
• Down the group (group 13): \(B

Set 3: \(Cl, I, Br, F\)

• \(F\) is in period 2, \(Cl\) in period 3, \(Br\) in period 4 and \(I\) in period 5.
• Down group 17: \(F

Set 4: \(N, B, Li, O\)

• Across period 2: \(Li\) (group 1) has larger radius than \(B\) (group 13), \(B\) has larger radius than \(N\) (group 15) and \(N\) has larger radius than \(O\) (group 16). So \(O

Answer:

1. \(Br < Ca < K
2. \(B < Ga < In < Tl\)
3. \(F < Cl < Br < I\)
4. \(O < N < B < Li\)