Properties Of D Block Elements

Most of the silver salts are insoluble except
So, is insoluble in water.

only exhibits green colour, other exhibits partial green colours / mixed green colours.

Most of the transition metal compounds (ionic as well as covalent) are coloured both in the solid state and in aqueous solution in contrast to the compounds of s and -block elements due to the presence of incomplete -subshell.

Step 1: There are four complete d-series.
Step 2: Each series contains 10 elements.

Step 1: Ionic size decreases with increasing nuclear charge.
Step 2: Order in option (B) is incorrect.

There are 4 complete d-series (3d, 4d, 5d, 6d incomplete), giving a total of 45 d-block elements.

Actinides like americium show a wide range of oxidation states due to participation of 5f electrons.

Step 1: Paramagnetic behaviour depends on the number of unpaired electrons.
Step 2: Electron configurations: V²+: d³, Cr²+: d⁴, Mn²+: d⁵, Fe²+: d⁶
Step 3: Number of unpaired electrons increases up to d⁵ and then decreases. ⟹ Fe²+ has fewer unpaired electrons than Mn²+ Hence the given order is incorrect.

Step 1: Understanding the Concept:
Enthalpy of atomization depends on the strength of the metallic bond. In transition metals, the strength of the metallic bond is generally proportional to the number of unpaired electrons available for interatomic metallic bonding.

Step 2: Detailed Explanation:
Let's look at the electronic configurations of the given 3d series elements ( and are valence electrons):
• Cr ( ): (6 valence electrons, 6 unpaired) - Very high enthalpy.
• Fe ( ): (8 valence electrons, 4 unpaired).
• Co ( ): (9 valence electrons, 3 unpaired).
• Ni ( ): (10 valence electrons, 2 unpaired). As we move from Cr to Ni, the number of unpaired electrons decreases because pairing starts in the subshell. Among the given options, Nickel (Ni) has the fewest unpaired electrons, leading to the weakest metallic bonding and thus the lowest enthalpy of atomization.

Step 3: Final Answer
The metal is Nickel (Ni), which has valence electrons.