Which of the following statement is wrong?

Options

A. In the lanthanide series the electrons occupy `4f`-orbitals in
preference to `5d` the and `6p`-orbitals.
B. Zero group was not present in the periodic table when Mendeleev presented it.
C. Law of octave was presented by Newland.
D. Cuprous compounds are coloured while cupric compounds are colourless.

Explanation

To determine which of the given statements is wrong, we will analyze each statement one by one.

### Step 1: Analyze the First Statement
**Statement 1:** In the lanthanide series, the electrons occupy 4f orbitals in preference to 5d and 6p orbitals.

- **Explanation:** The lanthanides are f-block elements, and their electronic configuration involves the filling of 4f orbitals. Electrons indeed fill the 4f orbitals before the 5d and 6p orbitals. Thus, this statement is **correct**.

### Step 2: Analyze the Second Statement
**Statement 2:** Zero group was not present in the periodic table when Mendeleev presented it.

- **Explanation:** At the time of Mendeleev's presentation of the periodic table, the noble gases (which are now classified as the zero group or group 18) had not been discovered. Therefore, this statement is also **correct**.

### Step 3: Analyze the Third Statement
**Statement 3:** The law of octaves was presented by Newland.

- **Explanation:** The law of octaves, which states that the properties of every eighth element are similar, was indeed formulated by John Newlands. Hence, this statement is **correct**.

### Step 4: Analyze the Fourth Statement
**Statement 4:** Cuprous compounds are colored while cupric compounds are colorless.

- **Explanation:** The cuprous ion (Cu⁺) has a completely filled d-orbital configuration (3d¹⁰), which means it has no unpaired electrons and is typically colorless. In contrast, the cupric ion (Cu²⁺) has an electronic configuration of 3d⁹, which means it has one unpaired electron and is colored. Therefore, this statement is **wrong**.

### Conclusion
The wrong statement among the options provided is **Statement 4**: "Cuprous compounds are colored while cupric compounds are colorless."

### Final Answer
**The correct answer is option 4.**

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