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Red phosphorus is less reactive than white phosphorus due to differences in their molecular structures and arrangements of atoms. White phosphorus consists of tetrahedral P4 molecules, each containing four phosphorus atoms bonded together in a highly strained, reactive structure. These P4 molecules are held together by weak van der Waals forces.

In contrast, red phosphorus has a polymeric structure, with long chains or layers of phosphorus atoms bonded together in a more stable arrangement. This structure makes it less prone to spontaneous combustion and less reactive with other substances compared to white phosphorus.

Additionally, white phosphorus is highly reactive because it readily reacts with oxygen in the air to form phosphorus pentoxide, producing intense heat and light, which can lead to spontaneous ignition. Red phosphorus, on the other hand, is much less reactive with oxygen and requires higher temperatures to ignite.

Nitrogen dioxide (NO2NO2) dimerizes to form dinitrogen tetroxide (N2O4N2O4) due to the presence of unpaired electrons on each nitrogen atom in the NO2NO2 molecule. This dimerization process is a result of the tendency of molecules with unpaired electrons to pair up and form more stable configurations.

In the gas phase, NO2NO2 exists predominantly as a reddish-brown dimer, N2O4N2O4, which is colorless. The dimerization reaction can be represented as:

2NO2⇌N2O42NO2⇌N2O4

This process is reversible, meaning that N2O4N2O4 can dissociate back into NO2NO2 molecules. The equilibrium between NO2NO2 and N2O4N2O4 depends on factors such as temperature, pressure, and concentration.

The dimerization of NO2NO2 to form N2O4N2O4 is an important reaction in atmospheric chemistry. In polluted urban environments, NO2NO2 is often emitted from vehicles and industrial sources. When NO2NO2 reacts with other pollutants and undergoes dimerization to form N2O4N2O4, it can contribute to the formation of smog and other harmful atmospheric conditions.

In H3PO2, also known as hypophosphorous acid, the oxidation number of hydrogen (H) is typically +1.

The sum of the oxidation numbers in a neutral molecule must equal zero. Since there are three hydrogen atoms, each with an oxidation number of +1, their total contribution is +3.

For oxygen (O), the typical oxidation number is -2, except in peroxides and when it's bonded to fluorine. In H3PO2, oxygen's oxidation number is -1.

Given that the overall charge of the molecule is zero, and knowing the oxidation numbers of hydrogen and oxygen, you can calculate the oxidation number of phosphorus (P).

Let's denote the oxidation number of phosphorus as xx:

(+1×3)+(−1×2)+x=0(+1×3)+(−1×2)+x=0

3−2+x=03−2+x=0

1+x=01+x=0

x=−1x=−1

So, in H3PO2, the oxidation number of phosphorus is -1.

The oxidation state of manganese (Mn) in its oxo-anion can be equal to its group number, which is +7. So, the formula of the oxo-anion would be MnO₄^(-), which is called permanganate ion.

The complex Co(NH3)5(NO2)2 exhibits two types of isomerism:

1. Coordination Isomerism: Coordination isomers occur when the ligands in a complex exchange places with anionic or neutral ligands outside the coordination sphere. In this complex, NO2 and NO3 can interchange positions, leading to the formation of coordination isomers.

2. Ionization Isomerism: Ionization isomers arise when there's a difference in the location of a ligand within a complex or between an ion and a molecule. In this case, the NO3^- ions in the coordination sphere can exchange positions with the NO3^- ions outside the coordination sphere.