The correct order of decreasing acidic nature of oxides

A binary compound of oxygen with another element is called oxide

Oxides can be simple (e.g., MgO, Al₂O₃ ) or mixed (Pb₃O₄ ,Fe₃O₄ ). Simple oxides can be classified on the basis of their acidic, basic or amphoteric character. An oxide that combines with water to give an acid is termed acidic oxide (e.g., SO₂ ,Cl₂O₇,CO₂ , N₂O₅ ). For example, SO₂ combines with water to give H₂SO₃ , an acid.

 The oxides which give a base with water are known as basic oxides (e.g., Na₂O, CaO, BaO). For example, CaO combines with water to give Ca(OH)₂, a base.

Some metallic oxides exhibit a dual behaviour. They show characteristics of both acidic as well as basic oxides. Such oxides are known as amphoteric oxides. They react with acids as well as alkalies. For example, Al₂O₃ reacts with acids as well as alkalies.

There are some oxides which are neither acidic nor basic. Such oxides are known as neutral oxides. Examples of neutral oxides are CO, NO and N₂O.

	Group 1	Group 2	Group 13	Group 14	Group 15
Period 2	Li	Be	B	C	N

According to periodic trend, the electronegativity of the period $2$ elements increases in the order :

$\mathrm{Li} < \mathrm{Be} < \mathrm{B} < \mathrm{C} < \mathrm{N}$

Electronegativty of the  central atom of the oxide is direclty proportional acidic nature of the oxide.

Therefore, the acidic character of their oxides decreases in the order as follows :

${\mathrm{N}}_2{\mathrm{O}}_3 > {\mathrm{CO}}_2 > {\mathrm{B}}_2{\mathrm{O}}_3 > \mathrm{BeO} > {\mathrm{Li}}_2\mathrm{O}$