Question

What is the symbol of ammonium ion?
(A) $N{O^ + }$
(B) $NH_4^ +$
(C) $N_3^ +$
(D) $O{H^ - }$

Answer 1

While writing the symbol for an ion, the one or two letter element symbol should be written first, followed by a superscript. The superscript has the number of charges on the given ion followed by a minus sign for negative ions or anions or a plus sign for positive ions or cations. Neutral atoms have a charge of zero, so there is no superscript for neutral atoms.

Complete answer:
The ammonium ion is a cation i.e. it is a positively charged ion with the chemical formula $NH_4^ +$ . It is obtained by the protonation of ammonia. Protonation also called hydronation is the process of addition of a proton to an atom, molecule or ion thus forming a conjugate acid. The ammonium ion has nitrogen atoms and hydrogen atoms in it. The ammonium ion is generally produced when the weak base ammonia reacts with a bronsted acid i.e. with a proton donor. The ammonium ion is a mildly acidic ion. When it reacts with bronsted base, it returns to the uncharged ammonia molecule.
Therefore, option B is the correct answer.

Note:
The nitrogen atom has five outer electrons, and another four from the four hydrogens. So, there are a total of nine electrons. Note that it is a positive ion as it loses one electron. This leaves a total of eight electrons in the outer level of the nitrogen. So, there are four pairs which are bonded to four hydrogen atoms. The ammonium ion is tetrahedral.