Question

Which choices contain an isoelectronic pair in the ground state? I. Cr*/Mn2+ II. Sc2*/V4+ III. Ca/T 24 IV. F/CI V. Ar/Rb a. I,II b. III, V c. II, IV d. I, V e. III, IV

Answer 1

The isoelectronic pairs in the ground state are I, II (Sc2+ and V4+) and III, V (Ca and Rb).

Step-by-step explanation:

An isoelectronic pair refers to two different atoms or ions that have the same number of electrons. In other words, they have the same electron configuration. To determine which choices contain an isoelectronic pair in the ground state, we need to compare the electron configurations of the given pairs.

From the provided choices, the isoelectronic pairs are:

a. I, II: Sc2+ and V4+ have the same electron configuration as they both have lost two electrons.

b. III, V: Ca and Rb have the same electron configuration as they both have lost two electrons.

Therefore, the correct choices are a. I, II and b. III, V.

Answer 2

The question asks to identify isoelectronic pairs, and the correct answer is option e. III, IV, which state that fluoride and chloride ions form an isoelectronic pair as they both have the electron configuration of neon after gaining one electron.

Step-by-step explanation:

The question asks about pairs of isoelectronic species, which means pairs of atoms or ions that have the same number of electrons. To determine if they're isoelectronic, we can look at the atomic number and the charge to count the electrons.

• Ca typically forms a Ca2+ ion by losing two electrons to attain a noble gas electron configuration, similar to argon.
• I typically forms an I− ion (iodide) by gaining one electron to also reach a noble gas electron configuration, like xenon.
• Fe can form multiple ions, including Fe2+ (ferrous) and Fe3+ (ferric) ions.

To address the choices given:

1. Cr*/Mn2+: Cr* presumably means a neutral Cr atom, which would not be isoelectronic with Mn2+ as they have different atomic numbers and hence different numbers of electrons.
2. Sc2+/V4+: Both ions have lost electrons from their neutral states, but since scandium and vanadium are different elements, they would not be isoelectronic as ions either.
3. Ca/Ti4+: As calcium usually forms a 2+ ion, this pair would not be isoelectronic either.
4. F/Cl: Each forms an anion by gaining one electron (F− and Cl−), thus making them isoelectronic, both having the electron configuration of neon.
5. Ar/Rb: Argon is a noble gas with a complete octet, whereas rubidium forms a Rb+ ion by losing one electron, thus not being isoelectronic with argon.

The correct choice is e. III, IV, where F/Cl form an isoelectronic pair.