Potassium (K)
Element 19 · alkali metal · group 1, period 4
Potassium is element 19, a alkali metal in group 1 and period 4. Its electron configuration is [Ar] 4s1. That leaves 1 valence electron in the outer shell, with the shells filling 2, 8, 8, 1. Losing its 1 valence electron is the shorter route to a full shell, so it carries a charge of +1.
- 19 protons
- 1 valence e−
- +1
- s-block
Potassium Lewis dot structure
Potassium has 1 valence electron, so its Lewis symbol carries 1 dot: one single dot. The ion has given those electrons away, which is why it is drawn in brackets with none.
Draw it in the Lewis structure generator →
Properties
| Atomic number | 19 |
|---|---|
| Symbol | K |
| Standard atomic weight | 39.098 u |
| Group | 1 |
| Period | 4 |
| Block | s-block |
| Category | alkali metal |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s1 |
| Noble-gas notation | [Ar] 4s1 |
| Electrons per shell | 2, 8, 8, 1 |
| Valence electrons | 1 |
| Common ionic charge | +1 |
| Electronegativity (Pauling) | 0.82 |
| Protons / electrons | 19 / 19 |
Electron configuration of potassium
Orbitals fill from the lowest energy upward. Writing that out for potassium gives 1s2 2s2 2p6 3s2 3p6 4s1, which is 1s2 2s2 2p6 3s2 3p6 4s1 in plain text.
Everything up to Ar is the same as in that noble gas, so it is usually abbreviated to [Ar] 4s1. The part outside the bracket is what does the chemistry.
| Subshell | Electrons | Capacity |
|---|---|---|
| 1s | 2 | 2 |
| 2s | 2 | 2 |
| 2p | 6 | 6 |
| 3s | 2 | 2 |
| 3p | 6 | 6 |
| 4s | 1 | 2 |
Potassium ion charge
Potassium commonly forms ions with a charge of +1.
It has 1 valence electron, so it is 7 short of a full octet and 1 above an empty outer shell. An atom takes whichever route is shorter, which is why the charge comes out as it does.
Common questions
What is the Lewis dot structure of potassium?
The symbol K with 1 dot, one for each valence electron: one single dot. Dots go one to a side before any pair up, the same way electrons fill separate orbitals before sharing one. The K+ ion is drawn in brackets with no dots, because it has lost them.
How many valence electrons does potassium have?
Potassium has 1 valence electron. For groups 1 and 2 the count is the group number, and potassium is in group 1.
What is the electron configuration of potassium?
1s2 2s2 2p6 3s2 3p6 4s1, or [Ar] 4s1 written from the previous noble gas. Orbitals fill lowest energy first.
What is the charge of potassium?
Potassium commonly forms ions with a charge of +1. With 1 valence electron it is 7 short of an octet and 1 above an empty shell, so it takes whichever route is shorter.
How many protons, electrons and neutrons does potassium have?
A neutral potassium atom has 19 protons and 19 electrons. Its standard atomic weight is 39.098, so the most common isotope has about 20 neutrons.
Nearby elements
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