Potassium (K)
Alkali metal
Potassium is a soft alkali metal that reacts even more energetically with water than sodium, igniting with a lilac flame. Its ions are indispensable to living cells, and most mined potassium becomes fertiliser.
Position on the periodic table
Atomic properties
| Atomic number | 19 |
|---|---|
| Atomic mass | 39.0983 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s1 |
| Noble gas shorthand | [Ar] 4s1 |
| Electrons per shell | 2, 8, 8, 1 |
| Valence electrons (outer shell) | 1 |
| Common oxidation states | +1 |
| Electronegativity (Pauling) | 0.82 |
| Covalent radius (approx.) | 203 pm |
| First ionization energy | 418.8 kJ/mol |
| Electron affinity | 48.4 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 0.862 g/cm³ |
| Melting point | 63.55 °C (336.7 K) |
| Boiling point | 758.85 °C (1032 K) |
| Appearance | silvery gray |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of potassium
Potassium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s1, usually shortened to [Ar] 4s1. Its electrons occupy 4 shells (2, 8, 8, 1), placing it in period 4 of the s-block. The 1 outer-shell electron drives its bonding behaviour. Explore it interactively in the electron configuration calculator.
Uses of potassium
- Potash fertilisers — over 90% of production
- Low-sodium salt substitutes
- Soap manufacturing (KOH)
- Gunpowder and fireworks (KNO₃)
Biological role: Essential — potassium ions maintain nerve impulses, heartbeat rhythm and fluid balance.
Occurrence: About 2.1% of the Earth's crust, mined from ancient evaporated sea beds.
Common compounds of potassium
KCl
Potassium chloride
KOH
Potassium hydroxide
KNO3
Potassium nitrate (saltpetre)
History and discovery
Discovered: 1807 — Humphry Davy. Name origin: From potash (plant ashes soaked in pots); the symbol K comes from Latin kalium.
Humphry Davy isolated potassium in 1807 by electrolysing molten potash — the first metal ever isolated by electricity.
Safety notes
Potassium metal ignites on contact with water and is stored under oil. Dietary potassium from food is essential and safe.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Potassium
1. What is the chemical symbol of Potassium?
2. What is the atomic number of Potassium?
3. Which category does Potassium belong to?
4. What is the state of Potassium at room temperature?
5. Which period of the periodic table is Potassium in?
Potassium FAQs
What is the atomic number of potassium?
Potassium's atomic number is 19 — every potassium atom has 19 protons in its nucleus.
What is the symbol for potassium?
K. From potash (plant ashes soaked in pots); the symbol K comes from Latin kalium.
Is potassium a metal, nonmetal, or metalloid?
Potassium is classified as a alkali metal.
What state is potassium at room temperature?
At about 25 °C, potassium is a solid. It melts at 63.55 °C.
How many valence electrons does potassium have?
Potassium has 1 electron in its outer shell (shell pattern: 2, 8, 8, 1).
What is potassium used for?
Key uses include: potash fertilisers — over 90% of production; low-sodium salt substitutes; soap manufacturing (koh).
Related elements
Keep working with this element
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