1.Isoelectronic species are
(A) K+, Cl-
(B) Na+, Cl-
(C) Na, Ar
(D)Na+, Ar

Dear student,

The species that have equal number of electrons in their shells are called as isoelectronic.
The atomic number of potassium is 19. Hence the number of electrons in K+ is 18.
the atomic number of Cl is 17. So the number of electrons with Cl- is 18.
Hence K+ and Cl- are isoelectronic.
The correct option is (A)
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