Potassium
Potassium (K, atomic number 19) is a Period 4 alkali metal (s-block, 39.098 u). Dominant intracellular cation (~140 mM in cytosol). Sets the resting membrane potential (≈ -70 mV) via K⁺ leak channels and repolarizes excitable neurons and cardiomyocyt
Potassium is a chemical element on the periodic table with the atomic symbol K, atomic number 19, and standard atomic weight 39.098 u. Classified as a Alkali Metal within Group 1 and Period 4 (s-block), potassium possesses a ground-state electron configuration of [Ar] 4s1 distributed across 4 concentric Bohr electron shells (2 · 8 · 8 · 1) with 1 outer-shell electrons. Dominant intracellular cation (~140 mM in cytosol). Sets the resting membrane potential (≈ -70 mV) via K⁺ leak channels and repolarizes excitable neurons and cardiomyocytes.
⚛️ Interactive Periodic Table Lab: Explore Potassium (K, Z = 19) in the CRV Science Dynamic Periodic Table & Bohr Orbital Lab to visualize its animated 2 · 8 · 8 · 1 electron shells, simulate live phase transitions from 0 K to 6,000 K, and compare periodic heatmaps across all 118 IUPAC elements.
Atomic Structure and Periodic Trends: How Do Quantum Orbitals Define Potassium?
Electron Shell Architecture and Ground-State Configuration
A neutral atom of potassium contains 19 protons in its atomic nucleus balanced by 19 electrons occupying quantized atomic orbitals. In the Bohr-Sommerfeld and quantum-mechanical orbital models, these electrons populate 4 principal energy shells (K (n=1): 2e−, L (n=2): 8e−, M (n=3): 8e−, N (n=4): 1e−), terminating in the spherical s-orbital (azimuthal quantum number l = 0) with ground-state configuration [Ar] 4s1. Removing the most loosely bound valence electron from an isolated gaseous potassium atom requires a first ionization energy of 419 kJ/mol, while its tendency to attract shared bonding electrons is quantified by a Pauling electronegativity of 0.82.
Periodic Table Position and Neighboring Elements
Within the periodic table, Potassium occupies Period 4, Group 1 of the s-block (Alkali Metals). Along Period 4, it is flanked by Argon (Ar, Z = 18) and Calcium (Ca, Z = 20). Vertically within its periodic family, Potassium shares valence orbital symmetry and homologous chemical trends with Lithium (Li), Sodium (Na), Rubidium (Rb), Cesium (Cs). Learners can interactively compare Potassium's orbital radii, ionization energy, and Pauling electronegativity against all neighboring elements in the Dynamic Periodic Table Lab.
Physical and Thermodynamic Properties: How Does Potassium Behave Across Temperature Regimes?
Standard Phase, Melting Point, and Boiling Point Dynamics
At standard ambient temperature and pressure (298.15 K / 25 °C, 1 atm), elemental potassium exists as a crystalline solid. As thermal energy increases, its crystal or molecular lattice undergoes solid-to-liquid fusion at a melting point of 336.7 K (+63.55 °C / +146.4 °F) and transitions to the vapor phase at a normal boiling point of 1,032 K (+758.85 °C / +1397.9 °F), spanning a liquid thermodynamic range of 695.30 K. In the CRV Science Dynamic Periodic Table, dragging the live temperature slider between absolute zero (0 K) and solar-photosphere temperatures (6,000 K) dynamically tracks Potassium's state transitions in real time alongside enthalpy and entropy phase equilibria.
Quantitative Atomic and Thermodynamic Parameter Matrix
| Parameter | Quantitative Value / Formula | Physical / Quantum Basis | Comparative Context in Group 1 / Period 4 |
|---|---|---|---|
| Atomic Number & Symbol | Z = 19 (K) | 19 nuclear protons; nuclear charge +19e | Located in Period 4, Group 1 (s-block) |
| Standard Atomic Weight | 39.098 u (g/mol) | Abundance-weighted isotopic nucleon mass | ~20 neutrons in dominant/reference mass number |
| Electron Configuration | [Ar] 4s1 | Shells: 2 · 8 · 8 · 1 (1 outer-shell e−) | Alkali Metals valence orbital architecture |
| Electronegativity & Ionization | χ = 0.82; IE1 = 419 kJ/mol | Pauling bond polarity scale & first valence ionization enthalpy | Governs covalent vs. ionic bond character |
| Melting & Boiling Points | MP: 336.7 K; BP: 1032 K | Cohesive lattice energy and intermolecular forces | STP (298 K) phase: SOLID (Liquid range: 695.30 K) |
| Principal Oxidation States | +1 | Valence electron donation, sharing, or acceptance | Discovered / First Isolated: 1807 |
Chemical Reactivity, Bonding, and Oxidation States: How Does Potassium Form Compounds?
Characteristic Oxidation States and Coordination Chemistry
As a Group 1 s-block alkali metal, it possesses a single loosely bound outermost s-electron outside a closed noble-gas core. This low first ionization enthalpy drives rapid one-electron oxidation to form monovalent +1 cations in ionic lattices and aqueous solutions. In chemical compounds, potassium exhibits characteristic oxidation states of +1. Depending on the electronegativity difference (Δχ) of its bonding partners—such as Oxygen (χ = 3.44), Fluorine (χ = 3.98), Chlorine (χ = 3.16), Nitrogen (χ = 3.04), Carbon (χ = 2.55), or Hydrogen (χ = 2.20)—potassium forms redox-specific oxides, halides, hydrides, or coordination complexes governed by Gibbs free energy (ΔG = ΔH − TΔS).
Nucleosynthesis, Discovery History, and Elemental Origins
First identified or isolated in 1807, Potassium carries a distinct cosmological and geochemical signature. As an element with atomic number Z ≤ 26, potassium is forged exothermically inside stars or via cosmic nucleosynthesis before being dispersed into protoplanetary nebulae.
Biological Role and Scientific Applications: Why Is Potassium Important in Nature and Technology?
Biochemical Classification: Essential Macro-Ion & Electrolyte
In comparative biochemistry and systems physiology, Potassium is classified as Essential Macro-Ion & Electrolyte. Major cellular ion regulating membrane action potentials, osmotic pressure, ATP chelation, and skeletal biomineralization. Across terrestrial and marine ecosystems, its chemical speciation interacts with cytosol, cell membrane, cellular homeostasis, adenosine triphosphate, cytosol.
Key Mechanistic Functions and Technological Uses
Dominant intracellular cation (~140 mM in cytosol). Sets the resting membrane potential (≈ -70 mV) via K⁺ leak channels and repolarizes excitable neurons and cardiomyocytes. Researchers and students can further investigate Potassium's functional role alongside all 118 elements by launching the Interactive Periodic Table & Element Detective Lab on CRV Science Learn.
Frequently Asked Scientific Questions
What is the electron configuration and valence shell structure of Potassium (K)?
Potassium (atomic number Z = 19) has the ground-state electron configuration [Ar] 4s1, distributing its 19 electrons across 4 shells as 2 · 8 · 8 · 1. Its outermost shell contains 1 electrons, placing Potassium in Group 1, Period 4 (s-block) as a member of the Alkali Metals. You can watch these 19 electrons orbit the nucleus in real time in the Dynamic Periodic Table Bohr Lab.
What phase of matter is Potassium at room temperature, and when does it melt or boil?
At standard room temperature (298 K / 25 °C) and 1 atm pressure, Potassium is a crystalline solid. It melts at 336.7 K (+63.55 °C / +146.4 °F) and boils at 1,032 K (+758.85 °C / +1397.9 °F). Using the 0–6,000 K temperature slider in the Interactive Periodic Table, you can observe Potassium's exact solid, liquid, and gas transitions relative to all other elements.
How does Potassium function in biochemistry, materials science, and technology?
Dominant intracellular cation (~140 mM in cytosol). Sets the resting membrane potential (≈ -70 mV) via K⁺ leak channels and repolarizes excitable neurons and cardiomyocytes. In biological systems, it is categorized under Essential Macro-Ion & Electrolyte, with principal oxidation states of +1 and a first ionization energy of 419 kJ/mol.