As per electronic configuration, the metal M is sodium(Na)...and it forms an oxide of formula Na2O....Hence option B is correct (M2O)

Electronic Configuration of Metal M:
The electronic configuration of metal M is given as:
1s2 2s2 2p6 3s1

Explanation:
1. Understanding Electronic Configuration:
The electronic configuration provides information about how electrons are distributed in different energy levels and orbitals of an atom. It follows the Aufbau principle, Pauli exclusion principle, and Hund's rule.

2. Aufbau Principle:
The Aufbau principle states that electrons fill the lowest energy orbitals first before moving to higher energy orbitals.

3. Pauli Exclusion Principle:
The Pauli exclusion principle states that each orbital can hold a maximum of two electrons with opposite spins.

4. Hund's Rule:
Hund's rule states that electrons occupy orbitals of the same energy level singly with parallel spins before pairing up.

5. Electronic Configuration of Metal M:
The given electronic configuration of metal M is 1s2 2s2 2p6 3s1. Let's break it down:
- The 1s orbital can hold a maximum of 2 electrons, so it is filled with 2 electrons (1s2).
- The 2s orbital can also hold a maximum of 2 electrons, so it is filled with 2 electrons (2s2).
- The 2p orbital can hold a maximum of 6 electrons, so it is filled with 6 electrons (2p6).
- Finally, the 3s orbital can hold a maximum of 2 electrons, but it has only 1 electron (3s1).

6. Formation of Oxide:
The formation of an oxide involves the combination of a metal with oxygen. Oxygen generally gains two electrons to achieve a stable electron configuration (8 electrons in the outermost energy level).

7. Valence Electrons of Metal M:
The valence electrons of metal M are the electrons in the outermost energy level, which is the 3s orbital. In this case, there is 1 valence electron.

8. Combination with Oxygen:
To achieve stability, metal M will lose its 1 valence electron to oxygen, which will gain 2 electrons. The metal cation formed will have a charge of +1, and the oxygen anion formed will have a charge of -2.

9. Formula of the Oxide:
Since the metal M loses 1 electron and oxygen gains 2 electrons, the ratio of metal to oxygen in the oxide will be 1:2. Therefore, the formula of the oxide will be M2O.

Conclusion:
The formula of the oxide of the metal M with the electronic configuration 1s2 2s2 2p6 3s1 is M2O. The metal M will lose 1 valence electron, forming a cation with a charge of +1, while oxygen will gain 2 electrons, forming an anion with a charge of -2. The resulting oxide will have a 1:2 ratio of metal to oxygen atoms, giving the formula M2O.