If they are soluble in water they give rise to alkaline solutions. Non-metals with electronegativity greater than 2.0 form acidic oxides. If these are soluble in water they give oxo-acids which are acidic. If the hydroxy compound is acidic, it will be written in the form H x XO y . Group 1 and Group 2.
Boron oxide is giant covalent and is acidic.
Carbon monoxide is molecular and is considered to be neutral. Silicon dioxide is giant covalent , containing single Si-O bonds. Lead monoxide is an ionic solid whose colour varies from yellow to orange. It is red when hot and turns back to yellow on cooling. On warming, these substances give off chlorine gas.