Element 19 · Alkali metal
Potassium (K) — Element 19
English potash
Potassium (K) is an alkali metal in Period 4, Group 1 of the periodic table with atomic number 19, standard atomic weight 39.098 u, and ground-state electron configuration [Ar] 4s¹. At standard temperature and pressure it is classified as a solid with 1 valence electron and common oxidation states +1.
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What are the atomic properties and physical constants of Potassium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 19
- Standard atomic mass
- 39.098 u
- Chemical family
- Alkali metal
- Ground-state configuration
- [Ar] 4s¹
- Electrons per shell
- 2, 8, 8, 1
- Valence electrons
- 1
- Common ion charges / oxidation states
- +1
- Phase at STP
- Solid
- Pauling electronegativity
- 0.82 Pauling
- First ionization energy
- 419 kJ/mol
- Atomic radius
- 243 pm
- Melting point
- 64 °C
- Boiling point
- 759 °C
- Discovery year
- 1807
- Table coordinate
- Period 4, Group 1
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Potassium’s shells?
A neutral Potassium atom contains 19 electrons distributed across 4 occupied principal energy shells ([Ar] 4s¹). The table below compares Potassium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in K | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 8 e⁻ | 18 e⁻ |
| n = 4 | N | 1 e⁻ | 32 e⁻ |
Frequently Asked Questions about Potassium (K)
What is the atomic mass and atomic number of Potassium (K)?
Potassium (K) has atomic number Z = 19 (19 protons in its nucleus) and an IUPAC standard atomic weight of 39.098 u. It sits in Period 4, Group 1 and is classified as an alkali metal.
What is the ground-state electron configuration of Potassium?
The neutral ground-state electron configuration of Potassium (Z = 19) is [Ar] 4s¹. Across its 4 occupied principal shells (n = 1 to n = 4), the electrons per shell are 2, 8, 8, 1, with 1 valence electron participating in bonding.
What are the common ion charges and electronegativity of Potassium?
Potassium commonly forms +1 oxidation states or ion charges in compounds. Its Pauling electronegativity is 0.82 and its first ionization energy is 419 kJ/mol.
When was Potassium discovered and what is it used for?
Potassium was discovered in 1807 (English potash). Fertilizer, nerve signals, soap
How does Potassium compare to neighboring elements?
Other alkali metal elements: