Consider the following oxides formed by elements from the s and p blocks: SO ₃ , Al ₂ O ₃ , CaO , and K ₂ O . Which of the following represents the correct increasing order of their basic character?

Step-by-step solution

The basic character of an oxide is directly related to the metallic character of its central element. Metallic character increases down a group and decreases across a period from left to right. The central elements are Sulphur (S), Aluminium (Al), Calcium (Ca), and Potassium (K). Sulphur is a non-metal, so SO ₃ is an acidic oxide. Aluminium is a metal/metalloid, and Al ₂ O ₃ is an amphoteric oxide. Calcium is a Group 2 metal, so CaO is a basic oxide. Potassium is a Group 1 metal, so K ₂ O is a strongly basic oxide.