Answer: hydrogen (H⁺) or hydronium (H₃O⁺) and hydroxide (OH⁻)
Explanation:
<u>1) Arrhenius definitions</u>
The chemist Svante Arrhenius, winner of the Noble Prize in chemistry by 1903, defined<em> acids and bases</em> based on the ability of such substances to give<em> ions</em> in water solutons.
<u>2) Acids</u>
Arrhenius defined an acid as a substance that dissociates in water to form <em>hydrogen ions (H⁺)</em>, also called protons. This process is called protonation (formation of protons). Due to its small size and high activity, H⁺ does not exist in that form, but it forms <em>H₃O⁺ ions</em> in aqueous solution.
<u>3) Bases</u>
Arrhenius defined a base as a substance that dissociates in water to form <em>hydroxide (OH⁻) ions.</em>
<u>4) Examples</u>
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That was the first definitions of acids and bases and is restricted to water solutions and does not include many compounds (like NH₃) which nowadays are identified as acids or bases.
Some examples of <em>Arrhenius acids and bases</em> are:
- KOH (aq) → K⁺ + OH⁻ (base becaue it produces OH⁻)
- H₂SO₄ (aq) → H⁺ + HSO₄⁻ (acid because ir produced H⁺)