Molecule Atom Colors – CPK Colors


CPK-Jmol Periodic Table

We’ve all seen models of molecules. Chemistry departments often have kits of plastic balls to stick together to represent atoms and their arrangement in molecules. These kits come with several different colors to easily distinguish one element from another. The choice of color for each atom is not arbitrary. There is a convention matching the color to the elements known as CPK colors.

The CPK part comes from the initials of the scientists who first used the colors to match the elements. Corey, Pauling, and Koltun. In 1952, Robert Corey and Linus Pauling used a basic color code with their models.

carbon – black
hydrogen – white
nitrogen – light blue
oxygen – red

This color scheme covers the atoms in a great majority of basic organic chemistry molecules, but obviously not all of them. Walter Koltun applied for a patent for a molecule set in 1962 to extend the color list to more elements.

Koltun’s list included

carbon – black
hydrogen – white
nitrogen – blue
oxygen – red
sulfur – yellow
phosphorus – purple
halogens – green – starting light green for fluorine and getting darker as you move down the group
metals – silver or gray

There is no set in stone standard for CPK color schemes, but nearly all molecule kits use the same common CPK colors. These colors are typically colors associated with some property of the elements. Sulfur is yellow, carbon is black, chlorine gas is green, iodine gas is purple. Others are less obvious. Nitrogen is found in the sky, and the sky is blue, therefore nitrogen atoms are blue. Oxygen is found in blood, blood is red so oxygen atoms are colored red.

Common CPK Coloring Chart

ElementColor
hydrogenwhite
carbonblack
nitrogendark blue
oxygenred
fluorine and chlorinegreen
brominedark red
iodinedark purple
noble gaseslight blue
phosphorusorange
sulfuryellow
boronlight orange
alkali metalspurple
alkaline earthsdark green
titaniumgray
irondark orange
whatever’s leftpink

Today, computers can generate visualizations of molecules with ease. Computers are not limited by the available colors. They can assign distinct colors to every element if they choose. One of the most common software molecule visualization software packages in use today is called Jmol.

Jmol has assigned colors to nearly every element you’re likely to find in a molecule and even a couple of common isotopes. These isotopes include hydrogen’s deuterium and tritium, carbon-13 and carbon-14 and nitrogen-15.

Download the PDF of the JMOL CPK Color Periodic Table showing these colors and their RGB and Hexadecimal values or just read the table below.

NumberElementRGB ColorHexadecimal Web Color
1H[255,255,255]FFFFFF
1D, H-2[255,255,192]FFFFC0
1T, H-3[255,255,160]FFFFA0
2He[217,255,255]D9FFFF
3Li[204,128,255]CC80FF
4Be[194,255,0]C2FF00
5B[255,181,181]FFB5B5
6C[144,144,144]909090
6C-13[80,80,80]505050
6C-14[64,64,64]404040
7N[48,80,248]3050F8
7N-15[16,80,80]105050
8O[255,13,13]FF0D0D
9F[144,224,80]90E050
10Ne[179,227,245]B3E3F5
11Na[171,92,242]AB5CF2
12Mg[138,255,0]8AFF00
13Al[191,166,166]BFA6A6
14Si[240,200,160]F0C8A0
15P[255,128,0]FF8000
16S[255,255,48]FFFF30
17Cl[31,240,31]1FF01F
18Ar[128,209,227]80D1E3
19K[143,64,212]8F40D4
20Ca[61,255,0]3DFF00
21Sc[230,230,230]E6E6E6
22Ti[191,194,199]BFC2C7
23V[166,166,171]A6A6AB
24Cr[138,153,199]8A99C7
25Mn[156,122,199]9C7AC7
26Fe[224,102,51]E06633
27Co[240,144,160]F090A0
28Ni[80,208,80]50D050
29Cu[200,128,51]C88033
30Zn[125,128,176]7D80B0
31Ga[194,143,143]C28F8F
32Ge[102,143,143]668F8F
33As[189,128,227]BD80E3
34Se[255,161,0]FFA100
35Br[166,41,41]A62929
36Kr[92,184,209]5CB8D1
37Rb[112,46,176]702EB0
38Sr[0,255,0]00FF00
39Y[148,255,255]94FFFF
40Zr[148,224,224]94E0E0
41Nb[115,194,201]73C2C9
42Mo[84,181,181]54B5B5
43Tc[59,158,158]3B9E9E
44Ru[36,143,143]248F8F
45Rh[10,125,140]0A7D8C
46Pd[0,105,133]006985
47Ag[192,192,192]C0C0C0
48Cd[255,217,143]FFD98F
49In[166,117,115]A67573
50Sn[102,128,128]668080
51Sb[158,99,181]9E63B5
52Te[212,122,0]D47A00
53I[148,0,148]940094
54Xe[66,158,176]429EB0
55Cs[87,23,143]57178F
56Ba[0,201,0]00C900
57La[112,212,255]70D4FF
58Ce[255,255,199]FFFFC7
59Pr[217,255,199]D9FFC7
60Nd[199,255,199]C7FFC7
61Pm[163,255,199]A3FFC7
62Sm[143,255,199]8FFFC7
63Eu[97,255,199]61FFC7
64Gd[69,255,199]45FFC7
65Tb[48,255,199]30FFC7
66Dy[31,255,199]1FFFC7
67Ho[0,255,156]00FF9C
68Er[0,230,117]00E675
69Tm[0,212,82]00D452
70Yb[0,191,56]00BF38
71Lu[0,171,36]00AB24
72Hf[77,194,255]4DC2FF
73Ta[77,166,255]4DA6FF
74W[33,148,214]2194D6
75Re[38,125,171]267DAB
76Os[38,102,150]266696
77Ir[23,84,135]175487
78Pt[208,208,224]D0D0E0
79Au[255,209,35]FFD123
80Hg[184,184,208]B8B8D0
81Tl[166,84,77]A6544D
82Pb[87,89,97]575961
83Bi[158,79,181]9E4FB5
84Po[171,92,0]AB5C00
85At[117,79,69]754F45
86Rn[66,130,150]428296
87Fr[66,0,102]420066
88Ra[0,125,0]007D00
89Ac[112,171,250]70ABFA
90Th[0,186,255]00BAFF
91Pa[0,161,255]00A1FF
92U[0,143,255]008FFF
93Np[0,128,255]0080FF
94Pu[0,107,255]006BFF
95Am[84,92,242]545CF2
96Cm[120,92,227]785CE3
97Bk[138,79,227]8A4FE3
98Cf[161,54,212]A136D4
99Es[179,31,212]B31FD4
100Fm[179,31,186]B31FBA
101Md[179,13,166]B30DA6
102No[189,13,135]BD0D87
103Lr[199,0,102]C70066
104Rf[204,0,89]CC0059
105Db[209,0,79]D1004F
106Sg[217,0,69]D90045
107Bh[224,0,56]E00038
108Hs[230,0,46]E6002E
109Mt[235,0,38]EB0026
110Dsunassigned
111Rgunassigned
112Cnunassigned
113Nhunassigned
114Flunassigned
115Mcunassigned
116Lvunassigned
117Tsunassigned
118Ogunassigned

CPK Color Sources:

Corey and Pauling’s original model description
Molecular Models of Amino Acids, Peptides, and Proteins
Robert B. Corey and Linus Pauling
Review of Scientific Instruments 24:8, 621-627

Walter Koltun’s US Patent
Space-filling atomic units and connectors for molecular models

Jmol Colors
http://jmol.sourceforge.net/jscolors/

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