To address the question regarding the mono cations N2+ and O2+, let's analyze each of the provided options to determine which statement is incorrect. Understanding the molecular orbital theory and the properties of these ions will help clarify the situation.
Examining Each Statement
1) In N2+, the N-N bond weakens
This statement is true. In the case of N2, the nitrogen-nitrogen bond is quite strong due to the triple bond formed by the overlap of atomic orbitals. When N2 loses an electron to form N2+, the bond order decreases because the removal of an electron from the bonding molecular orbital reduces the overall bond strength. Thus, the N-N bond does weaken in N2+.
2) In O2+, the O-O bond order increases
This statement is incorrect. In O2, the bond order is 2, indicating a double bond between the two oxygen atoms. When O2 loses an electron to form O2+, that electron is removed from a bonding molecular orbital, which decreases the bond order to 1.5. Therefore, the bond order does not increase; it actually decreases, making this statement false.
3) In O2+, paramagnetism decreases
This statement is accurate. O2 is known for its paramagnetic properties due to the presence of two unpaired electrons in its molecular orbital configuration. When it forms O2+, one of these unpaired electrons is removed, resulting in only one unpaired electron remaining. This reduction in unpaired electrons leads to a decrease in paramagnetism.
4) N2+ becomes diamagnetic
This statement is also true. N2 has a total of 10 electrons, and when it loses one electron to form N2+, it has 9 electrons. The molecular orbital configuration of N2+ results in all electrons being paired, which means N2+ is diamagnetic. Thus, this statement is correct.
Summary of Findings
From our analysis, the only incorrect statement is option 2: "In O2+, the O-O bond order increases." The bond order actually decreases when O2 forms O2+, as the removal of an electron from a bonding orbital weakens the bond. The other statements regarding N2+ and O2+ are accurate based on molecular orbital theory and the properties of these ions.
