speed of light in vacuum 299 792 458 m s

−1

Planck constant 6.626 070 15 x 10−34 J Hz −1

elementary charge

electron energy

proton mass

fine-structure constant 1/137.035 999

Rydberg constant 10 973 731.569 m−1

Boltzmann constant 1.380 65 x 10−23 J K−1

c

h

e

molar gas constant 8.314 5 J mol−1 K−1

electron volt 1.602 177 x 10-19 J 

(exact)

0.510 998 950 MeV

13.605 693 eV

R

R c

R

R

hc

mec

2

mp

1.602 176 634 x 10−19 C 

1.672 622 x 10−27 kg

3.289 841 960 x 1015 Hz

eV

k

P E R I O D I C T A B L E

Atomic Properties of the Elements

FREQUENTLY USED FUNDAMENTAL PHYSICAL CONSTANTS§

1 second = 9 192 631 770 periods of radiation corresponding to the 

transition between the two hyperfine levels of the ground state of 133Cs 

speed of light in vacuum 299 792 458 m s

−1

Planck constant 6.626 070 15 x 10−34 J Hz −1

elementary charge

fine-structure constant 1/137.035 999

Rydberg energy

Boltzmann constant 1.380 649 x 10−23 J K−1

c

h

e

electron volt 1.602 176 634 x 10-19 J 

(exact)

(exact)

(exact)

(exact)

(exact)

(exact)

R hc 13.605 693 1230 eV

1.602 176 634 x 10−19 C 

eV

k

Newtonian constant of 

gravitation

6.674 x 10−11 m3 kg−1 s

−2 G

 117

Ts

Tennessine

(294)

Solids

Artificially

Prepared

Liquids

Gases

58

Ce

Cerium

140.12

5.5386

°

Atomic

Number

Symbol

Name

Ground-state

Configuration

Ground 

State

Ionization

Energy (eV)

†

Based upon 12C. () indicates the mass number of the longest-lived isotope.

Standard

Atomic

Weight

†

(u)

 29

Cu

Copper

63.546

7.7264

 11

Na

Sodium

22.990

5.1391

 12

Mg

Magnesium

24.305

7.6462

 13

Al

Aluminum

26.982

5.9858

 14

Si

Silicon

 28.085

8.1517

 15

P

Phosphorus

30.974

10.4867

 16

S

Sulfur

 32.06

10.3600

 17

Cl

Chlorine

 35.45

12.9676

 18

Ar

Argon

39.948

15.7596

 1 2

S1/2

H

Hydrogen

1.008

13.5984

 4

Be

Beryllium

9.0122

9.3227

 37

Rb

Rubidium

85.468

4.1771

 55

Cs

Cesium

132.91

3.8939

 42

Mo

Molybdenum 95.95

7.0924

 41

Nb

Niobium

92.906

6.7589

 86

Rn

Radon

(222)

10.7485

 74

W

Tungsten

183.84

7.8640

 43

Tc

Technetium

(97)

7.1194

 75

Re

Rhenium

186.21

7.8335

 44

Ru

Ruthenium

101.07

7.3605

 76

Os

Osmium

190.23

8.4382

 45

Rh

Rhodium

102.91

7.4589

 77

Ir

Iridium

192.22

8.9670

 46

Pd

Palladium

106.42

8.3369

 78

Pt

Platinum

195.08

8.9588

 47

Ag

Silver

107.87

7.5762

 79

Au

Gold

196.97

9.2256

 48

Cd

Cadmium

112.41

8.9938

 80

Hg

Mercury

200.59

10.4375

 60

Nd

Neodymium

144.24

5.5250

 62

Sm

Samarium

150.36

5.6437

 63

Eu

Europium

151.96

5.6704

 64

Gd

Gadolinium

157.25

6.1498

 65

Tb

Terbium

158.93

5.8638

 61

Pm

Promethium

(145)

5.577

 66

Dy

Dysprosium

162.50

5.9391

 67

Ho

Holmium

164.93

6.0215

 68

Er

Erbium

167.26

6.1077

 69

Tm

Thulium

168.93

6.1843

 49

In

Indium

114.82

5.7864

 50

Sn

Tin

118.71

7.3439

 51

Sb

Antimony

121.76

8.6084

 52

Te

Tellurium

127.60

9.0097

 53

I

Iodine

126.90

10.4513

 81

Tl

Thallium

 204.38

6.1083

 82

Pb

Lead

207.2

7.4167

 83

Bi

Bismuth

208.98

7.2855

 84

Po

Polonium

(209)

8.414

 85

At

Astatine

(210)

 58

Ce

Cerium

140.12

5.5386

 59

Pr

Praseodymium

5.4702

 70

Yb

Ytterbium

173.05

6.2542

 90

Th

Thorium

232.04

6.3067

 92

U

Uranium

238.03

6.1941

 93

Np

Neptunium

(237)

6.2655

 94

Pu

Plutonium

(244)

6.0258

 95

Am

Americium

(243)

5.9738

 96

Cm

Curium

(247)

5.9914

 91

Pa

Protactinium

231.04

5.89

 97

Bk

Berkelium

(247)

6.1978

 98

Cf

Californium

(251)

6.2817

 99

Es

Einsteinium

(252)

6.3676

 100

Fm

Fermium

(257)

6.50

 101

Md

Mendelevium

(258)

6.58

 102

No

Nobelium

(259)

6.66

° ° °

° °

° °

°

°

° ° ° ° ° ° °

°

°

° °

° °

° ° ° ° °

 105 106 107 108 109 110 111 112

Db

Dubnium

(268)

Sg

Seaborgium

(269)

Hs

Hassium

(269)

Bh

Bohrium

(270)

Mt

Meitnerium

(278)

Ds

Darmstadtium

(281)

Rg

Roentgenium

(282)

°

1s

 114 116

 3

1s22s

Li

Lithium

 6.94

5.3917

 10

Ne

Neon

20.180

21.5645

 2

He

Helium

4.0026

24.5874

 9

O

Oxygen

15.999

13.6181

 8

F

Fluorine

18.998

17.4228

 7

N

Nitrogen

 14.007

14.5341

 6

C

Carbon

 12.011

11.2603

 5

B

Boron

 10.81

8.2980

 57

La

Lanthanum

138.91

5.5769

 89

Ac

Actinium

(227)

5.3802

 71

Lu

Lutetium

174.97

5.4259

 103

Lr

Lawrencium

(266)

4.96

 87

Fr

Francium

(223)

4.0727

 88

Ra

Radium

(226)

5.2784

 104

Rf

Rutherfordium

(267)

6.02

 72

Hf

Hafnium

178.49

6.8251

 40

Zr

Zirconium

91.224

6.6341

 39

Y

Yttrium

88.906

6.2173

 38

Sr

Strontium

87.62

5.6949

140.91

 56

Ba

Barium

137.33

5.2117

 73

Ta

Tantalum

180.95

7.5496

 54

Xe

Xenon

 131.29

12.1298

 19

K

Potassium

39.098

4.3407

 20

Ca

Calcium

40.078

6.1132

 21

Sc

Scandium

44.956

6.5615

 22

Ti

Titanium

47.867

6.8281

 30

Zn

Zinc

65.38

9.3942

 31

Ga

Gallium

69.723

5.9993

 32

Ge

Germanium

72.630

7.8994

 33

As Se

Arsenic

74.922

9.7886

 34

Selenium

78.971

9.7524

 35

Br

Bromine

79.904

11.8138

 36

Kr

Krypton

83.798

13.9996

 23

V

Vanadium

50.942

6.7462

 24

Cr

Chromium

51.996

6.7665

 25

Mn

Manganese

54.938

7.4340

 26

Fe

Iron

55.845

7.9025

 27

Co

Cobalt

58.933

7.8810

 28

Ni

Nickel

58.693

7.6399

Cn

Copernicium

(285)

Fl

Flerovium

(289)

Lv

Livermorium

(293)

NIST SP 966 (July 2019)

Period

1

6

5

4

3

2

7

For the most precise values and uncertainties visit ciaaw.org and pml.nist.gov/data.

2

S1/2

1s22s2

2

S1/2

2

S1/2

[Ne]3s2 [Ne]3s

1

S0

2

S1/2

1

S0

2

S1/2

1

S0

2

S1/2

1

S0

[Ar]4s2 [Ar]4s

[Kr]5s2 [Kr]5s

[Xe]6s2 [Xe]6s

[Rn]7s2 [Rn]7s

1

G4

[Xe]4f5d6s2

2

D3/2

3

F2

2

D3/2

3

F2

3

F2

3

F2

[Ar]3d4s2 [Ar]3d2

4s2

[Kr]4d5s2 [Kr]4d2

5s2

[Xe]4f145d26s2

[Rn]5f146d27s2

4

F3/2

7

S3

6

D1/2

7

S3

4

F3/2

5

D0

[Xe]4f145d36s2 [Xe]4f145d4

6s2

[Kr]4d45s [Kr]4d5

5s

[Ar]3d34s2 [Ar]3d5

4s

6

S5/2

5

D4

[Ar]3d54s2 [Ar]3d6

4s2

6

S5/2

6

S5/2

[Xe]4f145d56s2

[Kr]4d55s2

4

F9/2

[Ar]3d74s2

4

F9/2

[Kr]4d85s

3

F4

2

S1/2

5

F5

[Kr]4d75s

5

D4

[Xe]4f145d66s2

4

F9/2

[Xe]4f145d76s2

2

S1/2

[Kr]4d105s

1

S0

[Kr]4d10

3

D3

[Xe]4f145d96s

2

S1/2

[Xe]4f145d106s

1

S0

2

P1/2

1

S0

[Kr]4d105s2 [Kr]4d105s2

5p

[Xe]4f145d106s2

1

S0

[Hg]6p

2

P1/2

1s2

2s2

2p

1

S0

1s2

3

P0

1s2

2s2

2p2

4

S3/2

1s2

2s2

2p3

3

P2

1s2

2s2

2p4

2

P3/2

1s2

2s2

2p5

1

S0

1s2

2s2

2p6

2

P1/2

3

P0

4

S3/2

3

P2

2

P3/2

1

S0

3

P0

4

S3/2

3

P2

2

P3/2

1

S0

2

P1/2

3

P0

4

S3/2

3

P2

2

P3/2

1

S0

2

P1/2

3

P0

4

S3/2

3

P2

2

P3/2

1

S0

[Ar]3d104s2 [Ar]3d 4p 104s2 [Ar]3d84s2 [Ar]3d104s [Ar]3d104s24p2

[Kr]4d105s25p2

[Ar]3d104s24p3

[Kr]4d105s25p3

[Ar]3d104s24p4

[Kr]4d105s25p4

[Ar]3d104s24p5

[Kr]4d105s25p5

[Ar]3d104s24p6

[Kr]4d105s25p6

[Hg]6p2 [Hg]6p3 [Hg]6p4 [Hg]6p5 [Hg]6p6

2

D3/2

[Xe]4f145d6s2

1

S0

[Xe]4f146s2

[Ne]3s23p [Ne]3s2

3p2 [Ne]3s2

3p3 [Ne]3s2

3p4 [Ne]3s2

3p5 [Ne]3s2

3p6

[Xe]4f136s2 [Xe]4f126s2 [Xe]4f116s2 [Xe]4f106s2 [Xe]4f9

6s2 [Xe]4f75d6s2 [Xe]4f76s2 [Xe]4f66s2 [Xe]4f56s2 [Xe]4f46s2 [Xe]4f3

6s2 [Xe]4f5d6s2 [Xe]5d6s2

[Rn]5f147s2 [Rn]5f 7p 147s2 [Rn]5f137s2 [Rn]5f127s2 [Rn]5f117s2 [Rn]5f107s2 [Rn]5f97s2 [Rn]5f76d7s2 [Rn]5f77s2 [Rn]5f67s2 [Rn]5f46d7s2 [Rn]5f36d7s2 [Rn]5f26d7s2 [Rn]6d27s2 [Rn]6d7s2

2

D3/2

1

G4

2

D3/2

3

F2

4

I9/2

5

I4

5

I8

4

I15/2

° 4

I15/2

5

I8

6

H5/2

7

F0

8

S7/2

9

D2

6

H15/2

2

F7/2

3

H6

1

S0

2

F7/2

3

H6

9

D2

6

H15/2

7

F0

8

S7/2

6

L11/2

5

L6

4

K11/2

Lanthanides Actinides

Group

1

IA

2

IIA

3

IIIB

4

IVB

5

VB

6

VIB

7

VIIB

9

VIII

8 10 11

IB

12

IIB

13

IIIA

14

IVA

Physical Measurement Laboratory www.nist.gov/pml

Standard Reference Data www.nist.gov/srd

15

VA

16

VIA

17

VIIA

18

VIIIA

 113

 Nh

 Nihonium

(286)

 115

 Mc

 Moscovium

(289)

 118

Og

Oganesson

(294)

9.3175

6.8 7.8 7.7 7.6

[Rn]5f146d37s2 [Rn]5f146d4

7s2 [Rn]5f146d57s2

4

F3/2

[Rn]5f146d67s2

2

P1/2 °

0 5/2 4

§ For the most accurate 

values of these and 

other constants, visit 

pml.nist.gov/constants.

1

S0

1

S0

electron mass

proton mass

9.109 383 70 x 10−31 me kg

energy equivalent mec 0.510 998 950 MeV 2

mp 1.672 621 924 x 10−27 kg

energy equivalent mpc

2 938.272 088 MeV

Avogadro constant NA 6.022 140 76 x 1023 mol−1
NISTory of the Periodic Table

 1995

1988 

Cesium:

The frequency of microwave

radiation from this atom in

atomic clocks such as the 

NIST-F2 (2014), is used to 

define the second.

Potassium and

Rubidium:

JILA researchers married 

these elements into an 

ultracold gas of molecules 

and demonstrated striking 

predictions of quantum 

physics by hitting the atoms

with “rulers of light” known

as frequency combs

(Nobel Prize 2005) and 

trapping them in webs of

light known as optical lattices.

Deuterium:

This rare heavy 

isotope of hydrogen 

was concentrated at 

NIST and then identified

by Columbia University's 

Harold Urey (Nobel Prize 1934). On the 

left is a deuterium lamp; the light on the 

right comes from the NIST SURF III

Synchrotron Ultraviolet Radiation Facility.

Krypton:

Wavelengths of light from 

this atom, measured by NIST

researchers, defined the ocial 

meter until 1983.

Sodium:

NIST scientists used

lasers to cool a gas of

these atoms to more than

theoretically expected to

temperatures even closer 

to absolute zero. 

(Nobel Prize 1997) 

Rubidium:

These atoms were used by

researchers at JILA (NIST-CU Boulder)

to create the first Bose-Einstein 

condensate (Nobel Prize 2001). 

1931

1960

1967

2008

Design by: Natasha Hanacek/NIST

 2010

/2011

Individual ions of these 

atoms were probed in a 

NIST trap to create 

"quantum logic" clocks that 

measured the second more precisely than 

before and tested Einstein's general theory 

of relativity. Such quantum manipulations 

were recognized in the 2012 Nobel Prize.

Beryllium and

Aluminum:

Image Credit: NIST

Image Credit: H.Mark Helfer/NIST Image Credit: NIST/JILA/CU-Boulder

Image Credit: J. Amini/NIST

Image Credit: Steven Burrows and 

Ye/Jin groups/JILA

Image Credit: Neil Tucker/Wikimedia

Image Credit: Uwe Arp/NIST

www.nist.gov