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2. Consider the following pairs of ions:

A. [tex]\( Sc^{3+} \)[/tex] and [tex]\( Ti^{4+} \)[/tex]

B. [tex]\( Mn^{2+} \)[/tex] and [tex]\( Fe^{2+} \)[/tex]

C. [tex]\( Fe^{2+} \)[/tex] and [tex]\( Co^{3+} \)[/tex]

D. [tex]\( Cu^{+} \)[/tex] and [tex]\( Zn^{2+} \)[/tex]

Among these pairs of ions, isoelectronic pairs would include:

1. B, C, and D

2. A, C, and D

3. A, B, and D

4. A, B, and C



Answer :

GinnyAnswer
To determine which pairs of ions are isoelectronic (having the same number of electrons), we need to calculate the number of electrons in each ion.

1. Pair A: [tex]\( Sc^{3+} \)[/tex] and [tex]\( Ti^{4+} \)[/tex]
- Scandium (Sc): Atomic number is 21.
- [tex]\( Sc^{3+} \)[/tex] ion: 21 - 3 = 18 electrons.
- Titanium (Ti): Atomic number is 22.
- [tex]\( Ti^{4+} \)[/tex] ion: 22 - 4 = 18 electrons.
- So, the pair [tex]\( Sc^{3+} \)[/tex] and [tex]\( Ti^{4+} \)[/tex] are isoelectronic with 18 electrons each.

2. Pair B: [tex]\( Mn^{2+} \)[/tex] and [tex]\( Fe^{2+} \)[/tex]
- Manganese (Mn): Atomic number is 25.
- [tex]\( Mn^{2+} \)[/tex] ion: 25 - 2 = 23 electrons.
- Iron (Fe): Atomic number is 26.
- [tex]\( Fe^{2+} \)[/tex] ion: 26 - 2 = 24 electrons.
- So, the pair [tex]\( Mn^{2+} \)[/tex] and [tex]\( Fe^{2+} \)[/tex] are not isoelectronic (23 and 24 electrons respectively).

3. Pair C: [tex]\( Fe^{2+} \)[/tex] and [tex]\( Co^{3+} \)[/tex]
- Iron (Fe): Atomic number is 26.
- [tex]\( Fe^{2+} \)[/tex] ion: 26 - 2 = 24 electrons.
- Cobalt (Co): Atomic number is 27.
- [tex]\( Co^{3+} \)[/tex] ion: 27 - 3 = 24 electrons.
- So, the pair [tex]\( Fe^{2+} \)[/tex] and [tex]\( Co^{3+} \)[/tex] are isoelectronic with 24 electrons each.

4. Pair D: [tex]\( Cu^{+} \)[/tex] and [tex]\( Zn^{2+} \)[/tex]
- Copper (Cu): Atomic number is 29.
- [tex]\( Cu^{+} \)[/tex] ion: 29 - 1 = 28 electrons.
- Zinc (Zn): Atomic number is 30.
- [tex]\( Zn^{2+} \)[/tex] ion: 30 - 2 = 28 electrons.
- So, the pair [tex]\( Cu^{+} \)[/tex] and [tex]\( Zn^{2+} \)[/tex] are isoelectronic with 28 electrons each.

From the analysis, the isoelectronic pairs of ions are:
- Pair A: [tex]\( Sc^{3+} \)[/tex] and [tex]\( Ti^{4+} \)[/tex]
- Pair C: [tex]\( Fe^{2+} \)[/tex] and [tex]\( Co^{3+} \)[/tex]
- Pair D: [tex]\( Cu^{+} \)[/tex] and [tex]\( Zn^{2+} \)[/tex]

So, the correct answer is:
2) A, C and D