Question

1. which atom in each pair has the larger atomic radius? circle the correct answer.

a) li or k b) ca or ni c) ga or b d) cl or br
e) o or c f) be or b g) si or s h) fe or au

Explanation:

Step1: Analyze atomic radius trends

Atomic radius increases down a group (due to more electron shells) and decreases across a period (due to increasing nuclear charge pulling electrons closer).

a) Li or K

Li is in period 2, K in period 4. Since atomic radius increases down a group, K has a larger atomic radius.

b) Ca or Ni

Ca and Ni are in the same period (period 4). Ca is in group 2, Ni in group 10. As atomic radius decreases across a period, Ca has a larger atomic radius.

c) Ga or B

B is in period 2, Ga in period 4. Atomic radius increases down a group, so Ga has a larger atomic radius.

d) Cl or Br

Cl is in period 3, Br in period 4. Atomic radius increases down a group, so Br has a larger atomic radius.

e) O or C

O and C are in the same period (period 2). C is in group 14, O in group 16. As atomic radius decreases across a period, C has a larger atomic radius.

f) Be or B

Be and B are in the same period (period 2). Be is in group 2, B in group 13. As atomic radius decreases across a period, Be has a larger atomic radius.

g) Si or S

Si and S are in the same period (period 3). Si is in group 14, S in group 16. As atomic radius decreases across a period, Si has a larger atomic radius.

h) Fe or Au

Fe is in period 4, Au in period 6. Atomic radius increases down a group (and considering transition - metal trends where Au has more electron shells), Au has a larger atomic radius.

Answer:

a) K; b) Ca; c) Ga; d) Br; e) C; f) Be; g) Si; h) Au