Question

The acidic character of the oxides increases in the order:

• A. Na$_2$O $<$ MgO $<$ Al$_2$O$_3$ $<$ SiO$_2$ $<$ P$_2$O$_5$
• B. Na$_2$O $<$ Al$_2$O$_3$ $<$ MgO $<$ SiO$_2$ $<$ P$_2$O$_5$
• C. P$_2$O$_5$ $<$ SiO$_2$ $<$ Al$_2$O$_3$ $<$ MgO $<$ Na$_2$O
• D. Al$_2$O$_3$ $<$ SiO$_2$ $<$ MgO $<$ P$_2$O$_5$ $<$ Na$_2$O

Hint:

Acidic nature increases across a period and decreases down a group. Metal oxides are basic; non-metal oxides are acidic.