Is ammonia an acid or a base?

Is $\ce{NH_3}$ an acid or a base? N has a higher electro-negativity (3.04) than hydrogen (2.20), therefore nitrogen attracts the bond's electrons easily. The reaction should produce $\ce{H^+}$ because the electrons of hydrogen are attracted by nitrogen.

According to my Chemistry book, my assumption seems to be wrong because $\ce{NH_3}$ is considered a base. Why am I wrong?

• Oxygen has a higher electronegativity than nitrogen. Therefore, which reaction should be more likely: $$\ce{NH3 + H2O <=> NH4^+ + OH^-}$$ $$\ce{NH3 + H2O <=> H3O^+ + NH2^-}$$ This example only applies in water, of course, but $\ce{NH3}$ will act as a base in many other instances, also. – SendersReagent Mar 28 '16 at 11:22
• Indeed, $\ce{NH3}$ is an acid and a base, like water and many other compounds. – Ivan Neretin Mar 28 '16 at 12:02
• Ammonia is a base because it's lone pair on nitrogen accepta protons. Ammonia could act as a really weak acid. – Yunfei Ma Mar 28 '16 at 22:28