Which of the following correctly arranges the atoms and ions in order of increasing atomic radius: Se, Se2-, Te2-?
A
Se < Se2- < Te2-
B
Se2- < Se < Te2-
C
Te2- < Se < Se2-
D
Se < Te2- < Se2-
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1
Understand the concept of atomic radius: Atomic radius is the distance from the nucleus of an atom to the outermost electron shell. It generally increases as you move down a group in the periodic table and decreases across a period from left to right.
Consider the position of the elements in the periodic table: Selenium (Se) and Tellurium (Te) are in the same group (Group 16), with Tellurium being below Selenium. Therefore, Te has a larger atomic radius than Se due to the addition of electron shells.
Analyze the effect of ion formation on atomic radius: When an atom gains electrons to form an anion, its atomic radius increases due to increased electron-electron repulsion in the outer shell. Thus, Se2- will have a larger radius than Se.
Compare the atomic radii of Se, Se2-, and Te2-: Since Te is below Se in the periodic table, Te2- will have a larger radius than Se. Additionally, Se2- will have a larger radius than Se due to the gain of electrons.
Arrange the atoms and ions in order of increasing atomic radius: Based on the above analysis, the correct order is Se < Te2- < Se2-.