Multiple Choice
Which of the following statements correctly describes a trend in atomic radii in the periodic table?
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10. Periodic Properties of the Elements
Periodic Trend: Atomic Radius
Multiple Choice
Which of the following correctly ranks the atoms Rb, F, Mg, B, and N in order of decreasing atomic radius (largest to smallest)?
A
Rb > B > Mg > N > F
B
Mg > Rb > B > N > F
C
F > N > B > Mg > Rb
D
Rb > Mg > B > N > F
Verified step by step guidance1
Recall that atomic radius generally increases as you move down a group in the periodic table because additional electron shells are added, making the atom larger.
Recall that atomic radius generally decreases as you move from left to right across a period due to increasing nuclear charge pulling electrons closer to the nucleus.
Identify the positions of the atoms Rb, Mg, B, N, and F on the periodic table: Rb is in Group 1, Period 5; Mg is in Group 2, Period 3; B, N, and F are in Period 2 with B in Group 13, N in Group 15, and F in Group 17.
Use the trends to rank the atoms: since Rb is the furthest down and to the left, it has the largest radius; Mg is next down and left; B, N, and F are in the same period with radius decreasing from B to N to F due to increasing nuclear charge.
Combine these observations to write the order of decreasing atomic radius as: \(\mathrm{Rb} > \mathrm{Mg} > \mathrm{B} > \mathrm{N} > \mathrm{F}\).
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