Potassium ion

A potassium atom that has lost one electron, forming the positively charged ion K⁺. In aqueous and biological systems, K⁺ is the element’s predominant ionic form.

Potassium: A chemical element with atomic number 19, belonging to the alkali metals. Potassium ions form when potassium atoms lose their outermost electron.
Resting membrane potential: The voltage difference across a cell membrane when the cell is not actively signaling. Unequal K⁺ concentrations across the membrane help establish this voltage.
Atomic number: The number of protons in an atom’s nucleus, which identifies its chemical element. Potassium’s atomic number is 19, fixing the identity of its ion.
Sodium ion: A sodium atom that has lost one electron, forming the positively charged ion Na⁺. Na⁺ has the same charge as K⁺ but differs in size and membrane distribution.
Ion: An atom or molecule with a net electric charge because it has gained or lost electrons. K⁺ is a positively charged ion created by electron loss.
Action potential: A rapid, transient change in a cell’s membrane voltage that propagates along excitable membranes. K⁺ movement helps repolarize neurons and muscle cells after excitation.
Electron shell: A set of atomic orbitals grouped by principal energy level around a nucleus. Potassium loses its single outer-shell electron to form K⁺.
Rubidium ion: A rubidium atom that has lost one electron, forming the positively charged ion Rb⁺. Rb⁺ resembles K⁺ chemically and can substitute for it in some biological systems.
Ionic bond: An electrostatic attraction between oppositely charged ions. Potassium ions form ionic compounds by attracting negatively charged ions.
Sodium-potassium pump: A membrane protein that uses ATP to export sodium ions and import potassium ions. It maintains the concentration gradients that sustain cellular K⁺ levels.

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