Potassium
Table:
Potassium
Pronunciation	/pəˈtæsiəm/​(pə-TAS-ee-əm)
Appearance	silvery gray
Standard atomic weightAr, std(K)	39.0983(1)
Atomic number (Z)	19
Group	group 1: H and alkali metals
Period	period 4
Block	s-block
Element category	Alkali metal
Electron configuration	[Ar] 4s1

Electrons per shell

2, 8, 8, 1
Phase at STP	solid
Melting point	336.7 K ​(63.5 °C, ​146.3 °F)
Boiling point	1032 K ​(759 °C, ​1398 °F)
Density (near r.t.)	0.862 g/cm3
when liquid (at m.p.)	0.828 g/cm3
Critical point	2223 K, 16 MPa
Heat of fusion	2.33 kJ/mol
Heat of vaporization	76.9 kJ/mol
Molar heat capacity	29.6 J/(mol·K)
Oxidation states	−1, +1 (a strongly basic oxide)
Electronegativity	Pauling scale: 0.82
Ionization energies

1st: 418.8 kJ/mol
2nd: 3052 kJ/mol
3rd: 4420 kJ/mol
(more)

Atomic radius	empirical: 227 pm
Covalent radius	203±12 pm
Van der Waals radius	275 pm
Natural occurrence	primordial
Speed of sound thin rod	2000 m/s (at 20 °C)
Thermal expansion	83.3 µm/(m·K) (at 25 °C)
Thermal conductivity	102.5 W/(m·K)
Electrical resistivity	72 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+20.8·10−6 cm3/mol (298 K)
Young's modulus	3.53 GPa
Shear modulus	1.3 GPa
Bulk modulus	3.1 GPa
Mohs hardness	0.4
Brinell hardness	0.363 MPa
CAS Number	7440-09-7
Discovery and first isolation	Humphry Davy (1807)

Looking at the table, identify if the claim is entailed, neutral, or refuted. Conclude with JSON {"answer": "YOUR ANSWER"} — nothing else.

Hypothesis: Potassium was first discovered in the 18th century.

answer: refuted