1. Why do the Hydronium ion  and  the  Hydroxyl ion have  a positive charge  and negative charge respectively on itself ?

Asked by artee.misra | 1st Jun, 2021, 05:54: PM

Expert Answer:

Hydronium ions have positive charge because it is combination of H+ , which is just a proton and a water molecule. To understand this, look at the H2O molecule first. The oxygen atom has 6 protons and each of the hydrogen atoms have a proton. Hence the H2O molecule has a total of 8 positively charged protons. Oxygen has 6 valence electrons and each of the hydrogen’s have 1 valence electron, directly involved in covalent bonding with the oxygen atom. Hence the H2O molecule has a total of 8 negatively charged electrons. As the number of protons = number of electrons in the molecule, the molecule has no overall charge. When a lone proton forms a dative covalent bond with a lone pair on the oxygen atom of the H2O molecule, there are now overall 9 protons and still the same 8 valence electrons in the molecule. Hence due to the imbalance between protons and valence electrons in H3O, there is an overall positive charge on the molecule, hence why it exists as H3O+ when a lone proton (no electrons) bonds with H2O.
 
Just applying the similar concept in hydroxyl ions (OH-), It is having more electrons than protons so it will have negative charge on it.

Answered by Ravi | 3rd Jun, 2021, 08:36: PM