Draw a Lewis structure for NH4+ that obeys the octet rule, if possible, and answer the following questions based on your drawing: 1. Valence electrons of the central nitrogen atom. 2. The number of lone pairs on the central atom. 3. The number of single bonds. 4. The number of double bonds.
Chemistry · High School · Thu Feb 04 2021
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1. The central nitrogen atom in NH4+ (ammonium ion) has five valence electrons. However, due to the positive charge, we have to subtract one electron. Hence, the central nitrogen atom effectively has four valence electrons in the case of NH4+.
2. The number of lone pairs on the central nitrogen atom in NH4+ is zero. All valence electrons are used to form bonds with hydrogen atoms.
3. The number of single bonds in NH4+ is four. Each hydrogen atom forms a single bond with the nitrogen atom.
4. There are no double bonds in the NH4+ ion. All the bonds between the nitrogen and hydrogen are single bonds.
Extra: The Lewis structure is a diagram that represents the arrangement of the valence electrons among the atoms within a molecule. Here is how you would draw the Lewis structure for NH4+:
- Start by counting the total number of valence electrons. Nitrogen has 5 valence electrons, and each hydrogen atom has 1. However, since the molecule has a positive charge, you subtract one electron. Therefore, 5 (from nitrogen) + 4*1 (from each hydrogen) - 1 (positive charge) = 8 valence electrons to work with.
- Place the least electronegative atom in the center, which is the nitrogen in this case. Arrange the hydrogen atoms around it.
- Use the valence electrons to form single bonds (each bond is two electrons) between the central nitrogen atom and each of the hydrogen atoms.
- Check if you've used all valence electrons (you should have), and make sure every atom has a full octet (complete outer shell of electrons). In the case of hydrogen, a full outer shell is only 2 electrons, which is achieved with the single bond.
- In the case of the central nitrogen atom, it does not have non-bonding valence electrons or lone pairs left over after forming the four single bonds with hydrogen. So, there are no lone pairs on the nitrogen.
- In NH4+, nitrogen follows the octet rule as it shares eight electrons through its four bonds with the hydrogen atoms.
The Lewis structure for NH4+ should show a central nitrogen atom with four hydrogens symmetrically arranged around it, with no lone pairs on the nitrogen and no double bonds.