Another name of coordinate bond is the dative covalent bond. This bond is formed from two atoms sharing one pair of electrons. These atoms are usually held together because the pair of the electrons are attracted by the two nuclei. There are some occasions that simple covalent bonds are formed. In such situation, such bonds are formed when every particular atom donates one electron to form a bond. However, it is not mandatory that the atoms should be similar (Coordinate [Dative covalent] bonding para. 1). This is a covalent bond because it consists of pairs of electrons that are shared and those that are from one common atom.
Coordinate covalent bonds are mostly associated or occur in acids and basis. One example of a molecule that contains this bond is ammonium ions NH4+. Ammonium is a colorless gas (Kim 45). Ammonium ions are formed when the hydrogen ions that come from hydrogen chloride is transferred or moved to the molecule of ammonia from a single pair of electrons (Coordinate [Dative covalent] bonding para. 1). This happens when ammonia and hydrogen chlorides are mixed. This mixture results to chemical reactions that emits a white smoke referred to as solid ammonium chloride.
In the formation of ammonium Ion, the fourth hydrogen that comes from hydrogen chloride is joined or attached by a covalent bond [dative]. This is because; the hydrogen nucleus is the ones that is taken from chlorine and transformed into nitrogen. Therefore, electrons from hydrogen that is left by chlorine changed into negative chloride ions.
The moment the ammonium ions have been formed it becomes easier to differentiate between the ordinary covalent, bonds and the dative covalent. These can be represented on a diagram. In a diagram, electrons are normally shown differently but in reality the difference between these two electronics is nonexistence (Kim 45). It is also possible to show or demonstrated how a coordinate bond looks like in a diagram. An arrow is usually used to show this bond. The sharp arrow is directed or comes from an atom which gives/donates the single pair.
These ammonium ions can also be generated by reacting ammonia which is a weak base with bronsted acids.
H+ + NH3 → NH4+
Ammonium ions are also mildly acidic and when they react with bronsted which is a base they change to uncharged molecules of ammonia. Therefore, concentrated solutions of ammonia salts can be treated using strong bases like bronsted to produce ammonia. It is also possible to dissolve ammonia in water to produce or to convert small amounts of water into ammonium ions (Peifeng and Hui 21)
H3O+ + NH3 H2O + NH4+
One important factors that determines the degree to which ammonium is able to form into/change to ammonium ions is the pH of the solution. In case the pH of the solution is low, the equilibrium normally shifts to the right as more ammonia molecules are easily converted to the ammonium ions. On the other hand, when the pH of a solution is high meaning that that concentration of hydrogen ions is a bit low, the equilibrium normally shifts to the left. This implies that hydrogen ions hinder release of protons from the ammonium ions hence leading to generation of ammonia.
Ammonium compounds can also be formed or occur in vapor phases when hydrogen chloride vapor rise with the ammonia vapor. It is also possible to convert ammonium back to ammonia through addition of a strong base on it (Fux 17).
Coordinate [Dative covalent] bonding. Retrieved from: http://www.chemguide.co.uk/atoms/bonding/dative.html
Fux, Samuel et al. Accurate frozen-density embedding potentials as a first step towards a ubsystem description of covalent bonds, Journal of Chemical Physics, 132.16(2010): 16-25. Print.
Kim, Koo. Interplay of hydrogen-bond and coordinate covalent–bondinteractions in self- assembly of NH3 molecules on the Si (001) surface, Physical Review Letters [Phys Rev Lett], 100.25 (2008): 45-56. Print.
Peifeng Su and Hui Li. Energy decomposition analysis of covalent bonds and intermolecular interactions, Journal of Chemical Physics, 131.1(2009): 21-30. Print.