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# 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)