Among the following, the most basic oxide is:
A. $A{{l}_{2}}{{O}_{3}}$
B. ${{P}_{2}}{{O}_{5}}$
C. $Si{{O}_{2}}$
D. $N{{a}_{2}}O$

Hint: Basic oxides are those oxides which possess basic properties which contradict to that of the acidic oxides and react with water to make a base. They also react with a strong or weak acid to make a particular salt as well as water which is called neutralization reaction.

Complete step by step answer:
- In general, the electropositive character of the oxide's central atom will determine whether the oxides are going to be acidic or basic. The more electropositive the central atom will be the more basic will be the oxide. As the central atom becomes more electronegative, the acidic oxide's acidity increases.
- An oxide that mixes with water to give an acid is termed as an acidic oxide. The oxide that provides a base in water is termed as a basic oxide. An amphoteric solution may be a substance which will chemically react as either acid or base.

Classification Of Oxides are:
i.Acidic oxides.
ii. Basic oxides.
iii. Amphoteric oxides.
iv. Neutral oxides.
Now,
$N{{a}_{2}}O$ is that the most basic oxide.
$A{{l}_{2}}{{O}_{3}}$ is amphoteric in nature .
${{P}_{2}}{{O}_{5}}$ is acidic oxide.
$Si{{O}_{2}}$ is weakly acidic oxide.
So, the correct answer is “Option D”.

Note: Metal oxides are crystalline solids which consist of a metal cation and an oxide anion. They typically react with water to give bases or with acids to give salts. $MO+{{H}_{2}}O\to M{{(OH)}_{2}}$ (where M = group 2 metal) Thus, these compounds are often termed as basic oxides.
- Some examples of basic oxide are magnesium oxide which reacts with hydrochloric acid to give magnesium chloride , copper oxide which reacts with Nitric acid to give copper nitrate.