Sodium
Table:
Sodium
Appearance	silvery white metallic
Standard atomic weight Ar, std(Na)	22.98976928(2)
Atomic number (Z)	11
Group	group 1: H and alkali metals
Period	period 3
Block	s-block
Element category	Alkali metal
Electron configuration	[Ne] 3s1

Electrons per shell

2, 8, 1
Phase at STP	solid
Melting point	370.944 K ​(97.794 °C, ​208.029 °F)
Boiling point	1156.090 K ​(882.940 °C, ​1621.292 °F)
Density (near r.t.)	0.968 g/cm3
when liquid (at m.p.)	0.927 g/cm3
Critical point	2573 K, 35 MPa (extrapolated)
Heat of fusion	2.60 kJ/mol
Heat of vaporization	97.42 kJ/mol
Molar heat capacity	28.230 J/(mol·K)
Oxidation states	−1, +1 (a strongly basic oxide)
Electronegativity	Pauling scale: 0.93
Ionization energies

1st: 495.8 kJ/mol
2nd: 4562 kJ/mol
3rd: 6910.3 kJ/mol
(more)

Atomic radius	empirical: 186 pm
Covalent radius	166±9 pm
Van der Waals radius	227 pm
Natural occurrence	primordial
Speed of sound thin rod	3200 m/s (at 20 °C)
Thermal expansion	71 µm/(m·K) (at 25 °C)
Thermal conductivity	142 W/(m·K)
Electrical resistivity	47.7 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+16.0·10−6 cm3/mol (298 K)
Young's modulus	10 GPa
Shear modulus	3.3 GPa
Bulk modulus	6.3 GPa
Mohs hardness	0.5
Brinell hardness	0.69 MPa
CAS Number	7440-23-5
Discovery and first isolation	Humphry Davy (1807)

Consulting the table, determine whether the statement is entailed, neutral, or refuted. Conclude with JSON {"answer": "YOUR ANSWER"} — nothing else.

Sentence: Sodium was first discovered in the 19th century.

answer: entailed