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How does aqua regia dissolve gold?

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A diagram showing the periodic table entry for gold, with the symbol Au, atomic number 79, atomic weight 196.96657, electron configuration, and labels for its properties as a solid transition metal with a face-centered cubic crystal structure. — gold The precious metal gold is a chemical element with the symbol Au. Its square on the periodic table details some of its properties, including its atomic weight, atomic number, and crystal structure.

Aqua regia is a highly corrosive mixture typically composed of one part concentrated nitric acid and three parts concentrated hydrochloric acid by volume.1

While gold is known for its durability and resistance to most chemical reactions, this specific combination of acids is capable of dissolving it. The nitric acid acts as an oxidizing agent, while the hydrochloric acid provides chloride ions that react with the gold ions to form soluble chloroauric acid, effectively pulling the metal into solution. Because of this unique ability, alchemists historically named the mixture "royal water," as it could dissolve the "king of metals".123