Question

which one of the following is iso electronic with k+

(a) Ca
(b) Ar
(c) Ne
(d) Al

Answer 1

Isoelectronic species/ions/atoms are the species which have same number of electrons but different magnitude of nuclear charges & belongs to different atoms or ions.The isoelctronic ions with greater nuclear charge will have small size as compared to the ion with smaller nuclear charge.

(i) F– ion has 9 + 1 = 10 electrons. Thus, the species isoelectronic with it will also have 10 electrons. Some of its isoelectronic species are Na+ ion (11 – 1 = 10 electrons), Ne (10 electrons), O2– ion (8 + 2 = 10 electrons), and Al3+ ion (13 – 3 = 10 electrons).

(ii) Ar has 18 electrons. Thus, the species isoelectronic with it will also have 18 electrons. Some of its isoelectronic species are S2– ion (16 + 2 = 18 electrons), Cl– ion (17 + 1 = 18 electrons), K+ ion (19 – 1 = 18 electrons), and Ca2+ ion (20 – 2 = 18 electrons).

(iii) Mg2+ ion has 12 – 2 = 10 electrons. Thus, the species isoelectronic with it will also have 10 electrons. Some of its isoelectronic species are F– ion (9 + 1 = 10 electrons), Ne (10 electrons), O2– ion (8 + 2 = 10 electrons), and Al3+ ion (13 – 3 = 10 electrons).

(iv) Rb+ ion has 37 – 1 = 36 electrons. Thus, the species isoelectronic with it will also have 36 electrons. Some of its isoelectronic species are Br– ion (35 + 1 = 36 electrons), Kr (36 electrons), and Sr2+ ion (38 – 2 = 36 electrons).

Answer 2

Argon (Ar) is an isoelectronic with k+.

Option: (b)

Explanation:

• Potassium originally consists of 19 electron. Now when an electron is removed from the potassium atom, then the electron is known as the potassium ion.  

• The potassium ion consists of 18 electrons. It has 2, 8 and 8 electrons in the three consecutive orbital.

• An isoelectronic species is two radicles or atoms which have same number of electron.  

• Argon also has a total of 18 electron and it has its outermost orbital complete. So the two are isoelectronic species.

Learn more about isoelectronic species

What are isoelectronic species? how are there sizes vary in iso electronic series?

https://brainly.in/question/2536470

Explain why the size of isoelectronic species decreases with the increase in atomic number

https://brainly.in/question/8251563