Potassium (K): electron configuration, atomic mass and facts
Potassium (K) is element 19 of the periodic table, an alkali metal in period 4, group 1. Its electron configuration is [Ar] 4s1, with electrons arranged in shells 2, 8, 8, 1, and its standard atomic weight is 39.098 u.
💡 Reacts with water so fast the hydrogen ignites with a lilac flame.
▶ Watch Potassium’s electrons orbit in the interactive periodic tablePotassium at a glance
| Symbol | K |
|---|---|
| Atomic number | 19 |
| Atomic mass | 39.098 u |
| Category | Alkali metal |
| Group | 1 |
| Period | 4 |
| Block | s-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s1 |
| Noble-gas shorthand | [Ar] 4s1 |
| Electrons per shell | 2, 8, 8, 1 |
| Outer-shell electrons | 1 |
| Electronegativity (Pauling) | 0.82 |
| State at 20 °C | solid |
| Flame test colour | lilac |
Experiments with potassium
Where is Potassium on the periodic table?
Potassium is in period 4, group 1, in the s-block. The period number matches its 4 electron shells, and the block names the subshell its last electrons fill. In the same group, Sodium sits directly above it and Rubidium sits directly below it. Elements in one group have the same number of outer-shell electrons (1 here), which is why they react in similar ways.
How to work out the electron configuration of Potassium
Put 19 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s¹ (19). In shorthand, [Ar] stands for the 18 electrons of argon, giving [Ar] 4s¹.
How electronegative is Potassium?
Potassium has a Pauling electronegativity of 0.82, ranking 97 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Potassium in the virtual lab
Faradium’s chemistry workbench includes these chemicals that contain potassium: Potassium (small piece), Potassium chloride, Potassium nitrate, Potassium permanganate, Potassium chlorate, Potassium hydroxide, Potassium iodide, Potassium thiocyanate, Potassium dichromate, Iodine solution. Open the Chemistry Lab to experiment with them.
Frequently asked questions
What is the electron configuration of Potassium?
The electron configuration of Potassium (K) is 1s2 2s2 2p6 3s2 3p6 4s1. In noble-gas shorthand it is written [Ar] 4s1.
How many electrons does Potassium have in each shell?
Potassium has 19 electrons arranged in shells as 2, 8, 8, 1. It has 1 electron in its outer shell.
What is the atomic mass of Potassium?
The standard atomic weight of Potassium is 39.098 u, so one mole of Potassium atoms has a mass of about 39.098 g.
Is Potassium a metal?
Yes. Potassium is an alkali metal.
Explore nearby elements
More alkali metals: Lithium, Sodium, Rubidium, Caesium, Francium. See all elements on the periodic table.