Question

Which of the following is an isoelectronic series that the species are arranged in order of increasing radius?

A. K+ < Cl− < S2− < P3−

B. C< Si < Ge < Sn

C. O2− < S2− < Se2− < Te2−

D. B5− < Si4− < As3− < Te2−

Answer 1

C: O2− < S2− < Se2− < Te2−.

Step-by-step explanation:

The correct answer is option C: O2− < S2− < Se2− < Te2−.

In an isoelectronic series, the species have the same number of electrons but different atomic numbers. The trend of increasing radius can be explained by the number of electron shells and effective nuclear charge.

In this series, the species have an increasing number of electrons from left to right: O2− (with 10 electrons), S2− (with 16 electrons), Se2− (with 34 electrons), and Te2− (with 52 electrons).

As we move from left to right in a period of the periodic table, the number of protons in the nucleus increases, resulting in a stronger attractive force on the electrons. This leads to a decrease in the atomic radius.

Therefore, the radius of the species in the given isoelectronic series will increase as we move from O2− to Te2−. O2− will have the smallest radius, followed by S2−, then Se2−, and finally Te2− will have the largest radius.

To summarize, the isoelectronic series arranged in order of increasing radius is: O2− < S2− < Se2− < Te2−.