Multiple Choice
Which of the following correctly arranges the atoms and ions in order of increasing atomic radius: Se, Se2-, Te2-?
10. Periodic Properties of the Elements
Periodic Trend: Atomic Radius
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Which alkaline earth metal has the smallest atomic radius?
A
Ca
B
Rb
C
Na
D
Ra
E
Fr
Verified step by step guidance1
Identify the group of elements known as alkaline earth metals. These are located in Group 2 of the periodic table and include elements such as Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).
Understand that atomic radius generally increases as you move down a group in the periodic table. This is because each successive element has an additional electron shell, making the atom larger.
Examine the list of elements provided in the problem: Ca, Rb, Na, Ra, and Fr. Note that Rb (Rubidium), Na (Sodium), and Fr (Francium) are not alkaline earth metals; they belong to different groups.
Focus on the alkaline earth metals from the list: Ca (Calcium) and Ra (Radium). Compare their positions in the periodic table. Calcium is above Radium in Group 2.
Conclude that since atomic radius increases down a group, Calcium (Ca) will have a smaller atomic radius than Radium (Ra). Therefore, among the alkaline earth metals listed, Calcium has the smallest atomic radius.
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