Properties common to the elements manganese, iron, cobalt, nickel nad copper include the ready formation by them all of
(I) coloured ions in aqueous solution
(II)oxides of nitrogen are formed on reaction with concentrated `HNO_(3)`
(III) chlorides of formula `MCl_(2) and MCl_(3)`

Options

A. I, II, III
B. I, II
C. II, III
D. I only

Answer

To determine the properties common to the elements manganese, iron, cobalt, nickel, and copper, we will analyze each of the three given statements one by one.

### Step 1: Analyze the formation of colored ions in aqueous solution
- **Explanation**: Transition metals are known for forming colored ions in solution due to the presence of unpaired electrons in their d-orbitals. Manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) all have unpaired electrons in their d-orbitals, which allows for d-d transitions that result in the absorption of specific wavelengths of light, leading to the formation of colored solutions.
- **Conclusion**: This statement is true for all five elements.

### Step 2: Analyze the formation of oxides of nitrogen with concentrated HNO3
- **Explanation**: When transition metals react with concentrated nitric acid (HNO3), they typically produce nitrogen oxides as byproducts. For example, iron reacts with concentrated HNO3 to form iron nitrate and nitrogen dioxide (NO2). Similarly, copper reacts with concentrated HNO3 to produce copper nitrate and nitrogen dioxide (NO2) as well. This reaction is characteristic of these metals.
- **Conclusion**: This statement is also true for all five elements.

### Step 3: Analyze the formation of chlorides of formula MCl2 and MCl3
- **Explanation**: While manganese, iron, cobalt, and nickel can form both MCl2 and MCl3 due to their ability to exhibit +2 and +3 oxidation states, copper primarily exists in the +2 oxidation state and rarely forms CuCl3 (MCl3). Therefore, the formation of MCl3 is not common for copper.
- **Conclusion**: This statement is not true for all five elements.

### Final Conclusion:
Based on the analysis:
- Statement (I) is true for all elements.
- Statement (II) is true for all elements.
- Statement (III) is not true for all elements.

Thus, the properties common to manganese, iron, cobalt, nickel, and copper include:
- (I) Colored ions in aqueous solution
- (II) Oxides of nitrogen formed on reaction with concentrated HNO3

The correct answer is option 2.

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