Quick answerPotassium (K) is an alkali metal with atomic number 19 and an atomic mass of 39.098 (2023), in group 1, period 4. It was discovered by Humphry Davy in 1807. It is used for potash fertilisers and soft soap production. Its electron configuration is [Ar] 4s1.
Potassium is the quiet partner to sodium in your body: it keeps your heart beating steadily and your muscles firing. Farmers spread it as potash fertiliser to grow stronger crops, soap-makers use it for soft soaps, and fireworks borrow it for purple flames. Its radioactive isotope even helps scientists date ancient rocks.
Key facts
| Symbol | K |
|---|---|
| Atomic number | 19 |
| Atomic mass | 39.098 (IUPAC standard atomic weight, 2023) |
| Category | alkali metal |
| Group | 1 |
| Period | 4 |
| Block | s-block |
| Electron configuration | [Ar] 4s1 |
| Discovered | Humphry Davy, 1807 |
| Uses | potash fertilisers, soft soap production, fireworks, glass manufacturing, food processing |
Overview
Potassium is the quiet partner to sodium in your body: it keeps your heart beating steadily, your muscles firing and your nerves signalling. It has atomic number 19, an atomic mass of 39.098, and the electron configuration [Ar] 4s1, with a single outer electron it gives up easily. It sits in group 1, the alkali metals, in period 4. Humphry Davy isolated it in 1807 by passing an electric current through molten potash, and named it after potash, the ash of burned plants from which it came. Potassium never occurs as a free metal in nature; it is found in minerals and in seawater, and in every living cell, where it is the main ion inside cells while sodium dominates outside them. Farmers spread it as potash fertiliser to grow stronger crops, because plants need potassium to build roots, resist drought and ripen fruit. Soap-makers use it for soft soaps and liquid soaps, glass-makers add it to strengthen glass, and fireworks borrow it for purple flames. Its radioactive isotope, potassium-40, decays so slowly that geologists use it to date ancient rocks.
Frequently asked questions
What is potassium used for?
Potassium is mainly used as potash fertiliser, which helps crops grow stronger roots, resist drought and ripen fruit. It also makes soft soaps and liquid soaps, strengthens glass, and colours fireworks purple. In the body it keeps the heart beating and muscles firing, and its radioactive isotope helps date ancient rocks.
What is the symbol for potassium?
The chemical symbol for potassium is K, from its Latin name kalium, rather than from the English word potassium. It has atomic number 19 and a standard atomic mass of 39.098, and it sits in group 1 and period 4. Humphry Davy isolated it in 1807 from molten potash, the ash of burned plants.
What is the atomic number of potassium?
Potassium has atomic number 19, so it is the nineteenth element in the periodic table. Its atom holds nineteen protons and nineteen electrons, and its standard atomic mass is 39.098. It is an alkali metal in group 1 and period 4, with the electron configuration [Ar] 4s1, a single electron in its outer shell.
Is potassium a metal?
Yes, potassium is a metal, an alkali metal in group 1 of the periodic table. It is soft enough to cut with a knife and so reactive that it bursts into flame on contact with water, so it is stored under oil. It never occurs as a metal in nature, but only in compounds such as potash.
Why is potassium important for the body?
Potassium is essential for the body because it keeps the heart beating steadily, muscles contracting and nerves signalling. It is the main ion inside cells, balancing sodium outside them, and it helps control blood pressure and fluid levels. Bananas, potatoes, beans and leafy greens are all rich sources of potassium.
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Keep exploring
- Periodic table — all 118 elements
- Lithium (Li) — another alkali metal, atomic number 3
- Sodium (Na) — another alkali metal, atomic number 11
- Rubidium (Rb) — another alkali metal, atomic number 37
- Caesium (Cs) — another alkali metal, atomic number 55
- Francium (Fr) — another alkali metal, atomic number 87
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.