Question

Which of the elements form acidic oxide?

• A. Element with atomic number 11
• B. Element with atomic number 3
• C. Element with atomic number 15
• D. Element with atomic number 19

Answer 1

The correct option is C

Element with atomic number 15

Non-metals form acidic oxide whereas metals form basic oxides when they reacts with Oxygen ($O_2$).

e.g. -

$$\begin{gathered} \underset{\mathrm{Sodium}}{4\mathrm{Na}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Sodium}\mathrm{oxide}}{2{\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right)} \\ \underset{\mathrm{Sodium}\mathrm{oxide}}{{\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Sodium}\mathrm{hydroxide}}{2\mathrm{NaOH}\left(\mathrm{aq}\right)} \end{gathered}$$

So, here Sodium oxide(${\mathrm{Na}}_2\mathrm{O}$) is basic as it reacts with water to form a base Sodium hydroxide ($\mathrm{NaOH}$).

Explanation for correct option:

(C) Element with atomic number 15 is Phosphorus($\mathrm{P}$) which is a non-metal. Thus, its oxide is acidic in nature.

Explanation for incorrect options:

(A) Element with atomic number 11

Element with atomic number 11 is Sodium($\mathrm{Na}$) which is a metal.

(B) Element with atomic number 3

Element with atomic number 3 is Lithium($\mathrm{Li}$) which is also a metal.

(D) Element with atomic number 19

Element with atomic number 19 is Potassium($\mathrm{K}$) which is also a metal.

Therefore, the correct option is (C).