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.

Answer 1

The Correct Option is A

To establish the order of acidic strength among the provided oxides, their positions within the periodic table and resultant properties are examined:

1. Na$_2$O (Sodium Oxide): Classified as a basic oxide. Sodium, a Group 1 metal, characteristically forms basic oxides.
2. MgO (Magnesium Oxide): Also a basic oxide, but exhibits weaker basicity than Na$_2$O. Magnesium is an alkaline earth metal belonging to Group 2.
3. Al$_2$O$_3$ (Aluminum Oxide): Identified as an amphoteric oxide. Aluminum, a metalloid, forms oxides that display both acidic and basic characteristics.
4. SiO$_2$ (Silicon Dioxide): This oxide is acidic. Silicon, a Group 14 metalloid, yields acidic oxides such as SiO$_2$.
5. P$_2$O$_5$ (Phosphorus Pentoxide): Characterized as a highly acidic oxide. Phosphorus is a non-metal, and its oxides are strongly acidic.

The trend of increasing acidic character corresponds with progression across the periodic table from basic to acidic oxides. Consequently, the sequence of ascending acidic character is:

Na$_2$O $<$ MgO $<$ Al$_2$O$_3$ $<$ SiO$_2$ $<$ P$_2$O$_5$