Chemistry — Atomic Structure and Periodicity + 5 more topics

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Acids and bases are fundamental to chemistry. You'll primarily encounter them through the Brønsted-Lowry definition, where acids are proton (H⁺) donors and bases are proton acceptors.

When an acid dissolves in water, it donates a proton to water, forming a hydronium ion (H₃O⁺) and its conjugate base. For example:
$\text{HCl(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{H}_3\text{O}^+\text{(aq)} + \text{Cl}^-\text{(aq)}$

When chemicals react, they do so in specific, fixed ratios. Stoichiometry is the part of chemistry that deals with these quantitative relationships. It all starts with a balanced chemical equation.

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You encounter the three main states of matter (solid, liquid, gas) every day. The key difference between them is how their particles are arranged and how much energy they have.

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