Main Page

Welcome to the explain xkcd wiki!
We have an explanation for all 2 xkcd comics, and only 60 (2%) are incomplete. Help us finish them!

Latest comic

Go to this comic explanation

Chemical Formula

|< < Prev #3200 (January 28, 2026)

Title text: Some of the atoms in the molecule are very weakly bound.

|< < Prev Random Explanation

Explanation

The supposed "chemical formula for the universe" merely lists the numbers of atoms of each element. As is common practice for real compounds that contain organic structures or substructures, the numbers of atoms of carbon and hydrogen are listed before all of the others; the others are listed in alphabetical order. There are estimated to be 10⁸⁰ atoms of hydrogen (H), by far the most common element in the universe. The next most common element, helium (He), is a long way to the right in the list, and out of view, but would be about a third as many as the hydrogens.

These numbers are large, but they are not nameless. Using the long and short scales, these numbers can be described as:

Pos	Symb	Name	Quantity	Short Scale name	Long Scale name(s)	Ranked quantity*
1	C	Carbon	1076	Ten quattuorvigintillion	Ten thousand duodecillion Ten duodecilliard	4
2	H	Hydrogen	1080	One hundred quinvigintillion	One hundred tridecilllion	1
3	Ac	Actinium	1067	Ten unvigintillion	Ten undecillion	≈84
4	Ag	Silver	1069	One duovigintillion	One thousand undecillion One undecilliard	≈68
5	Al	Aluminium Aluminum	1075	One quattuorvigintillion	One thousand duodecillion One duodecilliard	14
6	Am	Americium	1026	One hundred septillion	One hundred quadrillion	≈84
7	Ar	Argon	1075	One quattuorvigintillion	One thousand duodecillion One duodecilliard	11
8	As	Arsenic	1070	Ten duovigintillion	Ten thousand undecillion Ten undecilliard	≈40
9	At	Astatine	1047	One hundred quattuordecillion	One hundred thousand septillion One hundred septilliard	≈84
10	Au	Gold	1069	One duovigintillion	One thousand undecillion One undecilliard	≈68
11	B	Boron	1071	One hundred duovigintillion	One hundred thousand undecillion One hundred undecilliard	≈61
12	Ba	Barium	1070	Ten duovigintillion	Ten thousand undecillion Ten undecilliard	≈33
13	Be	Beryllium	1071*	One hundred duovigintillion	One hundred thousand undecillion One hundred undecilliard	≈61
43*	He	Helium	1079*	Ten quinvigintillion	Ten tridecilllion	2
73*	O	Oxygen	1078*	One quinvigintillion	One tridecilllion	3

* - Information not provided by the comic; Source for ranked data, in particular, does not 'entirely' agree with the quantities that are given in the comic.

The matter originally created in the Big Bang was unbound protons and neutrons. In the first few minutes, some of these combined to form lightweight nuclei, but most remained as protons, i.e. the nuclei of hydrogen atoms. Other, more complex atoms formed later as a result of stellar nucleosynthesis, up to atomic mass 56. Still more massive nuclei have been formed via supernova nucleosynthesis. Although the proportions of these atoms depend in a complex way on the fusion processes involved, and on the stabilities of those nuclei, the most massive atoms are generally both less favored to form and short-lived, so their elemental abundances in the universe are very small. As shown above, the number of americium (Am) atoms is much smaller than those of any other element in the visible part of the "formula". There are slightly fewer atoms of americium in the entire universe than the total number of atoms of hydrogen and oxygen in 1.0 L of liquid water.

This may be poking some fun at the relative usefulness (or rather, uselessness) of chemical formulas for large organic molecules. While it is a useful concept for teaching people about chemistry and balancing equations, and it was useful in the early days of chemistry to try to categorize and learn about molecules via stoichiometry - it does not give much useful information. For example even the simple formula C₁₁H₁₅NO₂ has 302 registered isomers.^{[actual citation needed]} Many of them are NOT good to eat.^{[citation needed]}

The formula as it appears in the comic is truncated. The complete formula of the universe in this style (but arranged in order of abundance after carbon) would be C₁₀⁷⁷ H₁₀⁸⁰ He₁₀⁷⁹ O₁₀⁷⁸ Ne₁₀⁷⁶ N₁₀⁷⁶ Mg₁₀⁷⁵ Si₁₀⁷⁵ Ar₁₀⁷⁵ Fe₁₀⁷⁶ S₁₀⁷⁶ Ni₁₀⁷⁵ Ca₁₀⁷⁵ Al₁₀⁷⁵ B₁₀⁷¹ Be₁₀⁷¹ Na₁₀⁷⁵ As₁₀⁷² Br₁₀⁷² Li₁₀⁷² Cr₁₀⁷⁵ Ti₁₀⁷⁴ Mn₁₀⁷⁴ P₁₀⁷⁴ K₁₀⁷⁴ V₁₀⁷⁴ Cl₁₀⁷⁴ F₁₀⁷³ Sc₁₀⁷² Co₁₀⁷⁴ Cu₁₀⁷² Zn₁₀⁷³ Ga₁₀⁷² Ge₁₀⁷³ Se₁₀⁷² Kr₁₀⁷² Rb₁₀⁷² Sr₁₀⁷² Y₁₀⁷¹ Zr₁₀⁷² Nb₁₀⁷¹ Mo₁₀⁷¹ Tc₁₀⁰ Ru₁₀⁷¹ Rh₁₀⁷⁰ Pd₁₀⁷¹ Ag₁₀⁷⁰ Cd₁₀⁷¹ In₁₀⁷⁰ Sn₁₀⁷¹ Sb₁₀⁷⁰ Te₁₀⁷² I₁₀⁷¹ Xe₁₀⁷² Cs₁₀⁷⁰ Ba₁₀⁷² La₁₀⁷¹ Ce₁₀⁷² Pr₁₀⁷¹ Nd₁₀⁷² Pm₁₀⁰ Sm₁₀⁷¹ Eu₁₀⁷⁰ Gd₁₀⁷¹ Tb₁₀⁷⁰ Dy₁₀⁷¹ Ho₁₀⁷⁰ Er₁₀⁷¹ Tm₁₀⁷⁰ Yb₁₀⁷¹ Lu₁₀⁷⁰ Hf₁₀⁷⁰ Ta₁₀⁷⁰ W₁₀⁷⁰ Re₁₀⁷⁰ Os₁₀⁷¹ Ir₁₀⁷¹ Pt₁₀⁷¹ Au₁₀⁷⁰ Hg₁₀⁷¹ Tl₁₀⁷⁰ Pb₁₀⁷² Bi₁₀⁷⁰ Po₁₀⁰ At₁₀⁰ Rn₁₀⁰ Fr₁₀⁰ Ra₁₀⁰ Ac₁₀⁰ Th₁₀⁷⁰ Pa₁₀⁰ U₁₀⁷⁰ Np₁₀⁰ Pu₁₀⁰ Am₁₀⁰ Cm₁₀⁰ Bk₁₀⁰ Cf₁₀⁰ Es₁₀⁰ Fm₁₀⁰ Md₁₀⁰ No₁₀⁰ Lr₁₀⁰ Rf₁₀⁰ Db₁₀⁰ Sg₁₀⁰ Bh₁₀⁰ Hs₁₀⁰ Mt₁₀⁰ Ds₁₀⁰ Rg₁₀⁰ Cn₁₀⁰ Nh₁₀⁰ Fl₁₀⁰ Mc₁₀⁰ Lv₁₀⁰ Ts₁₀⁰ Og₁₀⁰ according to estimates of abundance.

The title text is probably referencing gravity, because for the most part most of mentioned atoms would be "held together" only by gravity, and it is a very weak bond indeed.

Transcript

[A long panel with a chemical formula trailing off the right side]

C_10⁷⁶ H_10⁸⁰ Ac_10⁶⁷ Ag_10⁶⁹ Al_10⁷⁵ Am_10²⁶ Ar_10⁷⁵ As_10⁷⁰ At_10⁴⁷ Au_10⁶⁹ B_10⁷¹ Ba_10⁷⁰ Be

[Caption below the panel:] The approximate chemical formula for the universe

Is this out of date? .

New here?

Last 7 days (Top 10)

Rank Score Pages Changes Username 1 22 18 22 TheusafBOT 2 16 13 16 Natg19 3 16 9 22 Elizium23 4 14 7 21 BunsenH 5 12 9 11 Qwertyuiopfromdefly 6 8 6 7 FaviFake 7 7 7 7 Victoria 8 7 5 6 Elektrizikekswerk 9 6 2 7 Megan 10 6 3 6 1234231587678

Lots of people contribute to make this wiki a success. Many of the recent contributors, listed above, have just joined. You can do it too! Create your account here.

You can read a brief introduction about this wiki at explain xkcd. Feel free to sign up for an account and contribute to the wiki! We need explanations for comics, characters, themes, memes and everything in between. If it is referenced in an xkcd web comic, it should be here.

• If you're new to wikis like this, take a look at these help pages describing how to navigate the wiki, and how to edit pages.

• Discussion about various parts of the wiki is going on at Explain XKCD:Community portal. Share your 2¢!

• List of all comics contains a table of most recent xkcd comics and links to the rest, and the corresponding explanations. There are incomplete explanations listed here. Feel free to help out by expanding them!

• We sell advertising space to pay for our server costs. To learn more, go here.

Rules

Don't be a jerk. There are a lot of comics that don't have set in stone explanations; feel free to put multiple interpretations in the wiki page for each comic.

If you want to talk about a specific comic, use its discussion page.

Please only submit material directly related to —and helping everyone better understand— xkcd... and of course only submit material that can legally be posted (and freely edited). Off-topic or other inappropriate content is subject to removal or modification at admin discretion, and users who repeatedly post such content will be blocked.

If you need assistance from an admin, post a message to the Admin requests board. <html><a href="https://plus.google.com/100547197257043990051" rel="publisher">Google+</a></html>