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From the following pairs of ions which one is not an iso-electronic pair?
medium
Chemical bonding and Molecular structure
2021
chemistry
Mn 2 + , ^{2+}, 2 + , Fe 3 + ^{3+} 3 +
Fe 2 + , ^{2+}, 2 + , Mn 2 + ^{2+} 2 +
Explanation To determine which pair of ions is not iso-electronic, we need to calculate the number of electrons in each ion. \\
Iso-electronic species have the same number of electrons. Let's analyze each option: \\
Option 1: O 2 − , ^{2-}, 2 − , F − ^{-} \\
−
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• Oxygen (O) has an atomic number of 8, so a neutral O atom has 8 electrons.
•
O
gains 2 electrons, so it has
electrons.
• Fluorine (F) has an atomic number of 9, so a neutral F atom has 9 electrons.
•
F
gains 1 electron, so it has
electrons.
Both ions have 10 electrons, so they are iso-electronic.
Option 2:
Na
Mg
• Sodium (Na) has an atomic number of 11, so a neutral Na atom has 11 electrons.
•
Na
loses 1 electron, so it has
11 − 1 = 10 11 - 1 = 10 11 − 1 = 10 electrons.
• Magnesium (Mg) has an atomic number of 12, so a neutral Mg atom has 12 electrons.
•
Mg
loses 2 electrons, so it has
12 − 2 = 10 12 - 2 = 10 12 − 2 = 10 electrons.
Both ions have 10 electrons, so they are iso-electronic.
Option 3:
Mn
Fe
• Manganese (Mn) has an atomic number of 25, so a neutral Mn atom has 25 electrons.
•
Mn
loses 2 electrons, so it has
25 − 2 = 23 25 - 2 = 23 25 − 2 = 23 electrons.
• Iron (Fe) has an atomic number of 26, so a neutral Fe atom has 26 electrons.
•
Fe
loses 3 electrons, so it has
26 − 3 = 23 26 - 3 = 23 26 − 3 = 23 electrons.
Both ions have 23 electrons, so they are iso-electronic.
Option 4:
Fe
Mn
•
Fe
has
26 − 2 = 24 26 - 2 = 24 26 − 2 = 24 electrons.
•
Mn
has
25 − 2 = 23 25 - 2 = 23 25 − 2 = 23 electrons.
These ions have different numbers of electrons, so they are not iso-electronic.
Therefore, the pair that is not iso-electronic is Option 4:
Fe
Mn