Identify the incorrect statement among the following .

Options

A. , Shielding power of 4f electrons is quite weak
B. There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu
C. Lanthanoid contraction is the accumulation of successive shrinkages
D. s a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements

Answer

To identify the incorrect statement among the given options, we will analyze each statement step by step.

### Step 1: Analyze Statement 1
**Statement 1:** The shielding power of 4f electron is quite weak.

- **Explanation:** The shielding power refers to the ability of inner electrons to shield the outer electrons from the nuclear charge. In the case of 4f electrons, they are located in the inner shell and are deeply buried. This means they do not effectively shield the valence electrons from the nucleus. Therefore, the statement is **true**.

### Step 2: Analyze Statement 2
**Statement 2:** There is a decrease in radii of the atom or ion as one proceeds from lanthanum to lutetium.

- **Explanation:** As we move from lanthanum (La) to lutetium (Lu), electrons are added to the 4f subshell. The 4f electrons have a weak shielding effect, leading to an increase in the effective nuclear charge (Z effective) experienced by the outer electrons. This results in a decrease in atomic and ionic radii. Therefore, this statement is also **true**.

### Step 3: Analyze Statement 3
**Statement 3:** The lanthanide contraction is the accumulation of the successive shrinkage.

- **Explanation:** The lanthanide contraction refers to the gradual decrease in size of the lanthanide series from lanthanum to lutetium due to the poor shielding effect of the 4f electrons. This results in a cumulative effect of size reduction, making this statement **true**.

### Step 4: Analyze Statement 4
**Statement 4:** As a result of lanthanide contraction, the properties of 4d series of the transition elements have no similarity with that of the 5d series of the elements.

- **Explanation:** The lanthanide contraction leads to a decrease in atomic radii of the 4d and 5d series, causing their properties to become more similar rather than dissimilar. Therefore, this statement is **false**.

### Conclusion
After analyzing all statements, we find that the incorrect statement is **Statement 4**.

### Final Answer
The incorrect statement is: **Statement 4** - "As a result of lanthanide contraction, the properties of 4D series of the transition elements have no similarity with that of the 5D series of the elements."

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