# Fundamental constants

## `periodictable.constants`

Various fundamental constants.

`periodictable.constants.``atomic_mass_constant` = 1.660538782e-27

  atomic mass constant (kg / u)

`periodictable.constants.``avogadro_number` = 6.02214179e+23

  Avogadro’s number (mol^-1)

`periodictable.constants.``electron_mass` = 0.000548577990946

  electron mass (u)

`periodictable.constants.``electron_radius` = 2.8179402894e-15

  electron radius r_e (m)

`periodictable.constants.``electron_volt` = 1.602176487e-19

  Electron volt (J/eV)

`periodictable.constants.``neutron_mass` = 1.00866491597

  neutron mass (u)

`periodictable.constants.``plancks_constant` = 4.13566733e-15

  Planck’s constant (eV s)

`periodictable.constants.``speed_of_light` = 299792458

  speed of light c (m/s)