Potassium (K)
Alkali metal · s-block · period 4 · group 1
Soft, silvery metal; tarnishes in seconds.
Potassium (symbol K) is chemical element number 19, a alkali metal in group 1, period 4 of the periodic table. Its standard atomic weight is 39.098 and its electron configuration is [Ar] 4s1. At room temperature it is a solid. Reacts with water even more violently than sodium, igniting the hydrogen with a lilac flame.
Properties
| Atomic number | 19 |
|---|---|
| Atomic mass | 39.098 |
| Category | Alkali metal |
| Block | s-block |
| Group · Period | 1 · 4 |
| Electron configuration | [Ar] 4s1 |
| Electrons per shell | 2, 8, 8, 1 |
| State at 25 °C | solid |
| Melting point | 336.53 K |
| Boiling point | 1032 K |
| Density | 0.862 g/cm³ |
| Electronegativity (Pauling) | 0.82 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1807 · Humphry Davy |
Key facts about Potassium
- Reacts with water even more violently than sodium, igniting the hydrogen with a lilac flame.
- Its symbol K comes from the Latin 'kalium'.
- A key nutrient for plants — the 'K' in N-P-K fertiliser.
- A natural radioactive isotope, potassium-40, is in every banana and in your body.
What Potassium is used for
Fertilisers, glass making, soaps, salt substitutes, heat-transfer alloys.
Where it sits in the periodic table
Potassium is in group 1, period 4, of the s-block. Its electron configuration [Ar] 4s1 means its outermost shell holds 1 electron, which is what places it here and explains much of its chemistry. See Potassium on the interactive table →
Potassium — frequently asked questions
What is Potassium used for?
Fertilisers, glass making, soaps, salt substitutes, heat-transfer alloys.
Is Potassium radioactive?
No. Potassium has at least one stable isotope and is not radioactive.
What is the electron configuration of Potassium?
Potassium has the electron configuration [Ar] 4s1, which is 2, 8, 8, 1 electrons per shell.
What group and period is Potassium in?
Potassium is in group 1, period 4, in the s-block. Its outer shell holds 1 electron.
Who discovered Potassium?
Potassium was discovered in 1807 by Humphry Davy.