Skip to main content
\(\require{cancel}\)
Physics LibreTexts

Appendix C: Fundamental Constants

Note: These constants are the values recommended in 2006 by CODATA, based on a least-squares adjustment of data from different measurements. The numbers in parentheses for the values represent the uncertainties of the last two digits.

* c  is the speed of light

Quantity Symbol Value
Atomic mass unit u

1.660 538 782 (83) x 10−27 kg

931.494 028 (23) MeV/c*

Avogadro’s number NA 6.022 141 79 (30) x 1023 particles/mol
Bohr magneton $$\mu_{B} = \frac{e \hbar}{2 m_{e}}$$ 9.274 009 15 (23) x 10−24 J/T
Bohr radius $$a_{0} = \frac{\hbar^{2}}{m_{e} e^{2} k_{e}}$$ 5.291 772 085 9 (36) x 10−11 m
Boltzmann’s constant $$k_{B} = \frac{R}{N_{A}}$$ 1.380 650 4 (24) x 10−23 J/K
Compton wavelength $$\lambda_{C} = \frac{h}{m_{e} c}$$ 2.426 310 217 5 (33) x 10−12 m
Coulomb constant $$k_{e} = \frac{1}{4 \pi \varepsilon_{0}}$$ 8.987 551 788... x 109 N • m2/C2 (exact)
Deuteron mass md

9.109 382 15 (45) x 10−31 kg

5.485 799 094 3(23) x 10−4 u

0.510 998 910 (13) MeV/c2 *

Electron mass me

9.109 382 15 (45) x 10−31 kg

5.485 799 094 3(23) x 10−4 u

0.510 998 910 (13) MeV/c2 *

Electron volt eV 1.602 176 487 (40) x 10−19 J
Elementary charge e 1.602 176 487 (40) x 10−19 C
Gas constant R 8.314 472 (15) J/mol • K
Gravitational constant G 6.674 28 (67) x 10−11 N • m2/kg2
Neutron mass mn

1.674 927 211 (84) x 10−27 kg

1.008 664 915 97 (43) u

939.565 346 (23) MeV/c2 *

Nuclear magneton $$\mu_{n} = \frac{e \hbar}{2 m_{p}}$$ 5.050 783 24 (13) x 10−27 J/T
Permeability of free space $$\mu_{0}$$ 4\(\pi\) x 10−7 T • m/A (exact)
Permittivity of free space $$\varepsilon_{0} = \frac{1}{\mu_{0} c^{2}}$$ 8.854 187 817... x 10−12 C2/N • m2 (exact)
Planck’s constant h 6.626 068 96 (33) x 10−34 J • s
Reduced Planck's constant $$\hbar = \frac{h}{2 \pi}$$ 1.054 571 628 (53) x 10−34 J • s
Proton mass mp

1.672 621 637 (83) x 10−27 kg

1.007 276 466 77 (10) u

938.272 013 (23) MeV/c2 *

Rydberg constant RH 1.097 373 156 852 7 (73) x 107 m−1
Speed of light in vacuum c 2.997 924 58 x 108 m/s (exact)

Useful combinations of constants for calculations:

  • hc = 12,400 eV • Å = 1240 eV • nm = 1240 MeV • fm
  • \(\hbar\)c = 1973 eV • Å = 197.3 eV • nm = 197.3 MeV • fm
  • kee2 = 14.40 eV • Å = 1.440 eV • nm = 1.440 MeV • fm
  • kBT = 0.02585 eV at T = 300 K

Contributors

  • The OpenStax College name, OpenStax College logo, OpenStax College book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the creative commons license and may not be reproduced without the prior and express written consent of Rice University. For questions regarding this license, please contact partners@openstaxcollege.org. Download for free at http://cnx.org/contents/031da8d3-b52...ed997733a@9.72.