**Electronic Configuration of Nitrogen in HNO2 (as per oxidation number)**

The electronic configuration of an element refers to the distribution of its electrons in different energy levels or orbitals. Nitrogen (N) belongs to the 2nd period of the periodic table and has an atomic number of 7. Therefore, the electronic configuration of nitrogen is 1s² 2s² 2p³.

However, in the compound HNO2 (nitrous acid), nitrogen exhibits a specific oxidation state, which affects its electronic configuration. The oxidation state of an atom is the hypothetical charge that an atom would have if all its bonds were purely ionic.

Let's break down the electronic configuration of nitrogen in HNO2 based on its oxidation number:

**1. Determine the Oxidation Number of Nitrogen:**
In nitrous acid (HNO2), the oxidation number of hydrogen (H) is +1 and oxygen (O) is -2. Since the overall charge of the compound is zero, we can calculate the oxidation number of nitrogen (N) using the following equation:
(+1) + (x) + (-2) = 0
Simplifying the equation, we find that the oxidation number of nitrogen is +3.

**2. Determine the Number of Electrons:**
To determine the electronic configuration of nitrogen in HNO2, we need to consider the atomic number of nitrogen (7) and its oxidation state (+3). The atomic number represents the total number of electrons in a neutral atom. Thus, in nitrogen with an oxidation state of +3, the number of electrons would be:
Atomic Number + Oxidation State = 7 + 3 = 10 electrons.

**3. Distribute Electrons in Energy Levels:**
Based on the number of electrons (10) and the Aufbau principle, we can distribute the electrons in different energy levels or orbitals. The Aufbau principle states that electrons fill orbitals starting from the lowest energy level to the highest.

The electronic configuration of nitrogen in HNO2, considering the oxidation number, can be represented as follows:

- 1s² 2s² 2p⁶: Represents the core electrons or those closest to the nucleus.
- 2p³: Represents the valence electrons, which are involved in chemical bonding.

Therefore, the electronic configuration of nitrogen in HNO2 is 1s² 2s² 2p³.

Oxidation number of N in HNO2 is 3.so electronic configuration of N is 1s2 2s2