Let's analyze each statement to identify which one is incorrect.

Statement 1: "Ozone is diamagnetic gas"

Diamagnetic substances are repelled by a magnetic field and have all electrons paired. The ozone molecule (O₃) has a bent structure with a bond order of 1.5. Its molecular orbital configuration shows it has no unpaired electrons, making it diamagnetic. This statement is correct.

Statement 2: "Ozone is violet-black in solid state"

Ozone in its gaseous state is pale blue, but in the solid state, it condenses to form a violet-black solid. This is a well-known physical property. This statement is correct.

Statement 3: "O₃ molecule is bent"

The ozone molecule has a bent or angular shape due to its central oxygen atom bonded to two other oxygen atoms with a bond angle of approximately 117°. This is a result of its electron geometry and lone pair repulsions. This statement is correct.

Statement 4: "ONCl and ONO^- are not isoelectronic"

Isoelectronic species have the same number of electrons and the same Lewis structure (same number of atoms and valence electrons). Let's calculate the total electrons for each:

• ONCl (Nitrosyl chloride): O (8) + N (7) + Cl (17) = 32 electrons
• ONO^- (Nitrite ion): O (8) + N (7) + O (8) + 1 (for the negative charge) = 24 electrons

They have different total electrons (32 vs 24) and different atomic compositions, so they are not isoelectronic. The statement says they are not isoelectronic, which is true. However, the question asks for the wrong statement. This statement is actually correct, meaning it is not wrong. But since the other three are also correct, we must re-check.

Wait, let's double-check the isoelectronic analysis. The nitrite ion ONO^- has N as central atom. Total valence electrons: N contributes 5, each O contributes 6, and the charge adds 1, so total valence electrons = 5 + 6 + 6 + 1 = 18. For ONCl: O contributes 6, N contributes 5, Cl contributes 7, total = 18. So both have 18 valence electrons and are isoelectronic with 3 atoms (like NO₂⁺, O₃, etc.). The statement says they are NOT isoelectronic, but they actually ARE isoelectronic. Therefore, this statement is wrong.

Final Answer: The wrong statement is "ONCl and ONO^- are not isoelectronic." because they are isoelectronic, both having 18 valence electrons and similar linear structures (though ONCl is bent due to lone pairs, but isoelectronic refers to same number of electrons).

Related Topics & Formulae

Isoelectronic Species: Species with the same number of electrons and same number of atoms. Example: CO₂ (22 electrons) and NO₂⁺ (22 electrons) are isoelectronic.

Ozone Properties: O₃ is diamagnetic, pale blue gas, violet-black solid, bent shape with bond angle ~117°.

Valence Electron Count: For molecules/ions, sum the valence electrons of all atoms and adjust for charge.