What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.
(i) F- (ii) Ar (iii) Mg2+ (iv) Rb+
Ions of different elements which have the same number of electrons but different magnitude of the nuclear charge are called isoelectronic ions.
(i) Since F- has 10 electrons, therefore N3- (7 + 3), O2- (8 + 2), Ne (10 + 0), Na+ (11 - 1), Mg2+ (12 - 2): Al3+ (13 - 3) are isoelectronic, as each one of these contains 10 electrons.
(ii) As Ar has 18 electrons, therefore P3- (15 + 3), S2- (16 + 2), Cl- (17 + 1), K+ (19 - 1), Ca2+ (20 - 2) are isoelectronic with it as cach one of each contains 18 electrons.
(iii) As Mg2+ has 10 electrons, therefore N3+ F , Ne, Na+, Al3+ are isoelectric with it as each one of these contains 10 electrons.
(iv) As Rb+ has 36 electron, therefore Br- (35 + 1), Kr (36 + 0) and Sr2+ (38 -2) are isoelectronic with it as each one of these contains 36 electrons.
Consider the following species : N3-, O2-, F-, Na+, Mg2+ and Al3+
(a) What is common in them?
(b) Arrange them in the order of increasing ionic radii.
Which of the following species will have the largest and the smallest size?
Mg, Mg2+, Al, Al3+.
In each of the following pairs, which species has a larger size? Explain.
(i) K or K+
(ii) Br or Br-
(iii) O2- or F-
(iv) Li+ or Na+
(v) P or As
(vi) Na+ or Mg2+
Give the formula of a species which will be isoelectronic with the following atoms or ions:
(i) Na2+
(ii) Cl-
(iii) Ca2+
(iv) Rb+.
