Introduction to Acids and Bases

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Acidic Adjective

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[uh-sid-ik]

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Acidic

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A property of a solution containing more hydrogen ions (H+) than hydroxide ions (OH-), resulting in a pH below 7.

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Example: The pH scale shows that substances with a pH value from 0 to 6 are acidic, with lower numbers indicating stronger acidity.

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Basic Adjective

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[bay-sik]

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Basic

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A property of a solution containing more hydroxide ions (OH-) than hydrogen ions (H+), resulting in a pH above 7.

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Example: This pH scale shows that basic (or alkaline) substances, like baking soda and bleach, have a pH value greater than 7.

Front

Alkaline Adjective

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[al-kuh-lahyn]

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Alkaline

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A synonym for basic, describing a substance or solution that has a pH greater than 7 due to excess hydroxide ions.

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Example: The pH scale shows that substances with a pH value from 8 to 14 are considered alkaline, which is the opposite of acidic.

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Hydronium ion Noun

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[hahy-droh-nee-uhm ahy-on]

Back

Hydronium ion

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The ion (H3O+) formed when a water molecule gains a hydrogen ion (H+), often used to represent H+ in water.

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Example: A water molecule (H₂O) uses a pair of its electrons to bond with a proton (H⁺), forming a positively charged hydronium ion (H₃O⁺).

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Hydroxide ion Noun

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[hahy-drok-sahyd ahy-on]

Back

Hydroxide ion

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The polyatomic ion (OH-) consisting of one oxygen and one hydrogen atom with a negative charge, characteristic of bases.

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Example: This image shows a hydroxide ion, which is made of one oxygen atom (O) and one hydrogen atom (H) bonded together, carrying an overall negative charge (⁻).

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Self-ionization Noun

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[self ahy-uh-ni-zey-shuhn]

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Self-ionization

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The process in which a substance, like water, spontaneously ionizes to form positive and negative ions without an external influence.

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Example: Two water molecules (H₂O) react to form a hydronium ion (H₃O⁺) and a hydroxide ion (OH⁻) in a reversible process.

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Arrhenius acid Noun

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[uh-ree-nee-uhs as-id]

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Arrhenius acid

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A substance that contains hydrogen and ionizes to produce hydrogen ions (H+) when it is dissolved in an aqueous solution.

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Example: An Arrhenius acid, like hydrochloric acid (HCl), is a substance that releases a hydrogen ion (H+) when dissolved in water, forming a hydronium ion (H₃O+).

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Arrhenius base Noun

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[uh-ree-nee-uhs beys]

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Arrhenius base

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A substance that contains a hydroxide group and dissociates to produce hydroxide ions (OH-) when dissolved in an aqueous solution.

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Example: An Arrhenius base is a substance that, when dissolved in water, increases the number of hydroxide (OH⁻) ions in the solution.

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Brønsted-Lowry acid Noun

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[bron-sted lou-ree as-id]

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Brønsted-Lowry acid

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A molecule or ion that acts as a hydrogen-ion (H+) donor in a chemical reaction with a corresponding base.

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Example: This diagram shows a Brønsted-Lowry acid (HA) donating a proton (H) to a Brønsted-Lowry base (B), which is the key definition.

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Brønsted-Lowry base Noun

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[bron-sted lou-ree beys]

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Brønsted-Lowry base

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A molecule or ion that acts as a hydrogen-ion (H+) acceptor in a chemical reaction with a corresponding acid.

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Example: The ammonia molecule (NH3) acts as a Brønsted-Lowry base by using its lone pair of electrons to accept a hydrogen ion from the water molecule.