Three Theories:
These two chemists on the left are, Johannes Nicolaus Brønsted and Thomas Martin Lowry. The Brønsted and Lowry theory states that acids are proton donors and bases are proton acceptors. When an acid and base react with each other, the acid forms its conjugate base, and the base forms its conjugate acid by the donation of a proton(H+).
Example:
HCl + H2O = H3O + Cl
In this example, HCl acts as an acid and donates a proton to the base (H2O). Once HCl and H2O have reacted, H3O is now a conjugate acid and Cl is the conjugate base.
Main points:
Example:
HCl + H2O = H3O + Cl
In this example, HCl acts as an acid and donates a proton to the base (H2O). Once HCl and H2O have reacted, H3O is now a conjugate acid and Cl is the conjugate base.
Main points:
- An acid is a proton (H+) donor.
- A base is a proton(H+) acceptor.
Svante Arrhenius, a swedish scientist, proposed that when acids and bases are dissolved in aqueous solutions, specific ions were created. The Arrhenius theory states that acids are defined as substances that disassociate in aqueous solutions to produce hydrogen ions (H+). Bases are defined as substances that disassociate in aqueous solutions to produce hydroxide ions (OH-).
Examples:
HCl → H+ and Cl-
HCl is an acid and in this example hydrochloric acid disassociates into hydrogen ions (H+) and Chlorine (Cl-) when dissolved in water.
NaOH →Na+ and OH-
NaOH is a base and in this example Sodium Hydroxide disassociates into Sodium (Na+) and hydroxide (OH-) ions when dissolved in water.
Main points:
Examples:
HCl → H+ and Cl-
HCl is an acid and in this example hydrochloric acid disassociates into hydrogen ions (H+) and Chlorine (Cl-) when dissolved in water.
NaOH →Na+ and OH-
NaOH is a base and in this example Sodium Hydroxide disassociates into Sodium (Na+) and hydroxide (OH-) ions when dissolved in water.
Main points:
- Acids dissolve in water to produce H+ ions.
- Bases dissolve in water to produce OH- ions.
Finally, an American chemist, Gilbert Lewis, made a theory stating acids (sometimes referred to as electrophiles) are electron pair acceptors and bases (sometimes referred to as nucleophiles) are electron pair donors.
Electrophiles - seekers of an additional electron pair.
Nucleophiles - donate electron pairs.
Example:
BF3 + NH3 → F3BNH3
In this example, BF3(base) donates and electron pair to NH3(acid) to produce a new compound F3BNH3.
Main points:
Electrophiles - seekers of an additional electron pair.
Nucleophiles - donate electron pairs.
Example:
BF3 + NH3 → F3BNH3
In this example, BF3(base) donates and electron pair to NH3(acid) to produce a new compound F3BNH3.
Main points:
- An acid is an electron pair acceptor.
- A base is an electron pair donor.