An acid donates hydrogen ions in solution, has a pH below 7, and reacts with metals and bases.
A chemical element is a pure substance made of only one type of atom, identified by its atomic number.
Key definitions and terms across chemistry topics for quick lookup and concept reinforcement.
An atom is the smallest unit of an element, made up of protons, neutrons, and electrons.
A mixture combines two or more substances physically without chemical bonding, separable by physical means.
A chemical reaction transforms reactants into new products through the breaking and forming of chemical bonds.