<p>Both of them.</p>

<p>The composition of the atmosphere, crust, mantle, core and bulk earth are all notably different.</p>

<p>The atmosphere is composed of ~78% nitrogen and ~21% oxygen, with small amounts of other gases.</p>

<p><a href="https://i.sstatic.net/cGwUy.gif" rel="noreferrer"><img src="https://i.sstatic.net/cGwUy.gif" alt="enter image description here"></a></p>

<p>The bulk composition of the earth by weight is mostly, iron, oxygen, silicon and magnesium, in that order, with all the other elements making up only about 5% of the earth's weight. Most of the earth's iron is in the core, which is about 85% iron. The rest of the earth is dominated by oxygen and silicon, primarily in the form of silicate minerals, which consist of $\ce{SiO4^{4-}}$ tetrahedra linked in different ways and with different cations filling in the gaps.</p>

<p><a href="https://i.sstatic.net/ajURi.jpg" rel="noreferrer"><img src="https://i.sstatic.net/ajURi.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2016-03-07T20:03:55.813Z
Note that the pie charts are by mass. Different pie charts would result if the elements were expressed in terms of molar fraction. In that sense, oxygen is the most abundant element on the Earth (including the atmosphere), while iron by more than a factor of three.
David Hammen
CC BY-SA 3.0
2016-03-08T00:27:45.333Z
What does "bulk silicate earth" mean?
naught101
CC BY-SA 3.0
2016-03-08T04:16:42.253Z
@naught101 crust + mantle
Gimelist
CC BY-SA 4.0
2018-10-18T21:42:02.610Z
This seems like a good answer, but could you add a source please? That would also make clear if we speak about numbers or mass fractions.
AtmosphericPrisonEscape
CC BY-SA 4.0
2022-10-27T08:02:24.593Z
@AtmosphericPrisonEscape See, for instance, [Wang et. al _Icarus_ **2018**, 299, 460.](https://doi.org/10.1016/j.icarus.2017.08.024) for mantle, core and bulk.
Kexanone
CC BY-SA 3.0
2016-03-07T16:01:38.200Z
2016-03-07T16:01:38.200Z
bon
<p>"How can this be reconciled?"  In two words: silicon dioxide :-)  </p>

<p>Yes, that's simplistic, but reflects the fact that virtually all the oxygen occurs in chemical combinations with other elements, not as free oxygen.   The same is true for other elements in the crust &amp; mantle.</p>

CC BY-SA 3.0
2016-03-08T04:15:56.983Z
Actually, silicon oxide (as quartz or other silica minerals) is only that common in the uppermost part of the crust. There is hardly any silica, if at all, more than a few tens of km deep
Gimelist
CC BY-SA 3.0
2016-03-08T05:07:59.157Z
Unless you are talking about normative oxide analysis, Michael, instead of quarts and other mineral forms. There is a lot of silicon bonded to oxygen that is counted as silicon dioxide.
haresfur
CC BY-SA 3.0
2016-03-08T07:52:50.317Z
And also MgO, CaO, Al2O3, FeO and whatever. Singling out SiO2 out of all oxides misses the point.
Gimelist
CC BY-SA 3.0
2016-03-08T22:03:38.437Z
@Michael: No, it makes a point (though maybe you missed it :-)), which is that virtually all the oxygen is bound up in compounds.  Indeed, the only reason there's a significant amount of free oxygen in the atmosphere is photosynthesis.
jamesqf
CC BY-SA 3.0
2016-03-09T01:51:12.377Z
@jamesqf in compounds that are not necessarily silicon oxide. Therefore, there is no reason to single it out. Read my previous comment.
Gimelist
CC BY-SA 3.0
2016-03-10T23:13:51.540Z
This is interesting and I'm going to spin off as a new question.
haresfur
CC BY-SA 3.0
2016-03-07T19:06:49.953Z
2016-03-07T19:06:49.953Z
jamesqf
<p>When I was in school, I was taught that we need oxygen to breathe, but it actually constitutes only a small fraction of the atmospheric composition, and that nitrogen constituted the largest fraction of the atmosphere's composition.</p>

<p><a href="https://www.google.co.uk/?gfe_rd=cr&amp;ei=3pXdVtz-NYvS8Aelgb_oDg&amp;gws_rd=ssl#q=most+abundant+element+on+earth" rel="noreferrer">This quick Google search</a> mentions oxygen as the most abundant element.</p>

<p>How can this be reconciled?</p>

CC BY-SA 3.0
2016-03-07T14:53:07.117Z
Where does Google say this? https://en.wikipedia.org/wiki/Atmosphere_of_Earth
Torbjørn T.
CC BY-SA 3.0
2016-03-07T14:53:36.140Z
https://www.google.co.uk/?gfe_rd=cr&ei=3pXdVtz-NYvS8Aelgb_oDg&gws_rd=ssl#q=most+abundant+element+on+earth
Matthew Layton
CC BY-SA 3.0
2016-03-07T14:56:03.010Z
It isn't strictly speaking Google that says it. Anyways, that page describes Earth's *mass*, not its atmosphere.
Torbjørn T.
CC BY-SA 3.0
2016-03-07T14:59:47.703Z
Further, judging by https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust compared to https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Abundance_of_elements_in_the_Earth it looks like the site Google highlights actually refers to the crust, not the entire earth.
Torbjørn T.
CC BY-SA 3.0
2016-03-07T16:17:24.747Z
By mass? Please write better questions (the title is not even a question). [Edit] it and put in the actual quote.
Jan Doggen
CC BY-SA 3.0
2016-03-08T04:19:03.997Z
That's because rocks are mostly made out of oxygen (by volume, atomic proportions, and mostly by mass as well). It's a bit weird considering that oxygen is a gas, but when you combine it with most other elements it kind of "glues" them together as solids.
Gimelist
CC BY-SA 3.0
2016-03-09T15:25:56.740Z
Earth's atmosphere is just a tiny part of the Earth as a whole. Your teacher talked about the atmosphere only, where oxygen isn't the most abundant. In the planet as a whole, oxygen dominates by far (or, taken by mass, iron - oxygen is still second, though). Look around you - all of that soil, rock etc. is most likely formed of oxygen. Also, look at the oceans - all that water contains huge amounts of oxygen (1:2 by part, 8:1 by mass).
Luaan
CC BY-SA 3.0
2016-03-10T16:32:35.997Z
No, it's (surmised to be) iron. Please edit the title to include the word *atmosphere* or *crust*.
Mazura
CC BY-SA 4.0
2018-10-18T21:33:01.683Z
Look at the dang stars in the Universe.  Stars are composed of mainly hydrogen.  The vast clouds of star stuff out there is hydrogen. No one quoted hydrogen?
stormy
CC BY-SA 3.0
2018-04-09T16:43:15.890Z
Perhaps a better question would be: What happened to the carbon, neon and nitrogen when you compare "surmised" Milky Way abundances versus "surmised" Earth abundances? Just orbiting the sun in interplanetary space?
Jack R. Woods
CC BY-SA 3.0
2018-04-09T16:48:49.370Z
I am presuming that Jupiter is expected to mirror solar system abundances so my comment above would pertain to the zone where terrestrial bodies were formed.
Jack R. Woods
CC BY-SA 3.0
2018-04-09T17:16:38.033Z
Proposed answer to my own question: It was blown away by solar event that cleared most of the solar system after the formation of the terrestrial planets. (It's somewhere "out there".)
Jack R. Woods
<atmosphere><geochemistry><nitrogen><oxygen>
Is oxygen the most abundant element on Earth?
Matthew Layton
# Is oxygen the most abundant element on Earth?

(Asked by: username_0 on 2016-03-07)

When I was in school, I was taught that we need oxygen to breathe, but it actually constitutes only a small fraction of the atmospheric composition, and that nitrogen constituted the largest fraction of the atmosphere's composition.

[This quick Google search](https://www.google.co.uk/?gfe_rd=cr&ei=3pXdVtz-NYvS8Aelgb_oDg&gws_rd=ssl#q=most+abundant+element+on+earth) mentions oxygen as the most abundant element.

How can this be reconciled?

**Tags:** atmosphere, geochemistry, nitrogen, oxygen

> **Comments:**
> **username_1**: Where does Google say this? https://en.wikipedia.org/wiki/Atmosphere_of_Earth  
> **username_0**: https://www.google.co.uk/?gfe_rd=cr&ei=3pXdVtz-NYvS8Aelgb_oDg&gws_rd=ssl#q=most+abundant+element+on+earth  
> **username_1**: It isn't strictly speaking Google that says it. Anyways, that page describes Earth's *mass*, not its atmosphere.  
> **username_1**: Further, judging by https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust compared to https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Abundance_of_elements_in_the_Earth it looks like the site Google highlights actually refers to the crust, not the entire earth.  
> **username_2**: By mass? Please write better questions (the title is not even a question). [Edit] it and put in the actual quote.  
> **username_3**: That's because rocks are mostly made out of oxygen (by volume, atomic proportions, and mostly by mass as well). It's a bit weird considering that oxygen is a gas, but when you combine it with most other elements it kind of "glues" them together as solids.  
> **username_4**: Earth's atmosphere is just a tiny part of the Earth as a whole. Your teacher talked about the atmosphere only, where oxygen isn't the most abundant. In the planet as a whole, oxygen dominates by far (or, taken by mass, iron - oxygen is still second, though). Look around you - all of that soil, rock etc. is most likely formed of oxygen. Also, look at the oceans - all that water contains huge amounts of oxygen (1:2 by part, 8:1 by mass).  
> **username_5**: No, it's (surmised to be) iron. Please edit the title to include the word *atmosphere* or *crust*.  
> **username_7**: Perhaps a better question would be: What happened to the carbon, neon and nitrogen when you compare "surmised" Milky Way abundances versus "surmised" Earth abundances? Just orbiting the sun in interplanetary space?  
> **username_7**: I am presuming that Jupiter is expected to mirror solar system abundances so my comment above would pertain to the zone where terrestrial bodies were formed.  
> **username_7**: Proposed answer to my own question: It was blown away by solar event that cleared most of the solar system after the formation of the terrestrial planets. (It's somewhere "out there".)  
> **username_6**: Look at the dang stars in the Universe.  Stars are composed of mainly hydrogen.  The vast clouds of star stuff out there is hydrogen. No one quoted hydrogen?  

---

## 2 answers

### Answer by username_8 on 2016-03-07. Score: 12

Both of them.

The composition of the atmosphere, crust, mantle, core and bulk earth are all notably different.

The atmosphere is composed of ~78% nitrogen and ~21% oxygen, with small amounts of other gases.

[![enter image description here](https://i.sstatic.net/cGwUy.gif)](https://i.sstatic.net/cGwUy.gif)

The bulk composition of the earth by weight is mostly, iron, oxygen, silicon and magnesium, in that order, with all the other elements making up only about 5% of the earth's weight. Most of the earth's iron is in the core, which is about 85% iron. The rest of the earth is dominated by oxygen and silicon, primarily in the form of silicate minerals, which consist of $\ce{SiO4^{4-}}$ tetrahedra linked in different ways and with different cations filling in the gaps.

[![enter image description here](https://i.sstatic.net/ajURi.jpg)](https://i.sstatic.net/ajURi.jpg)

> **Comments:**
> **username_9**: Note that the pie charts are by mass. Different pie charts would result if the elements were expressed in terms of molar fraction. In that sense, oxygen is the most abundant element on the Earth (including the atmosphere), while iron by more than a factor of three.  
> **username_10**: What does "bulk silicate earth" mean?  
> **username_3**: @username_10 crust + mantle  
> **username_11**: This seems like a good answer, but could you add a source please? That would also make clear if we speak about numbers or mass fractions.  
> **username_12**: @username_11 See, for instance, [Wang et. al _Icarus_ **2018**, 299, 460.](https://doi.org/10.1016/j.icarus.2017.08.024) for mantle, core and bulk.  

---

### Answer by username_13 on 2016-03-07. Score: 2

"How can this be reconciled?" In two words: silicon dioxide :-)

Yes, that's simplistic, but reflects the fact that virtually all the oxygen occurs in chemical combinations with other elements, not as free oxygen. The same is true for other elements in the crust & mantle.

> **Comments:**
> **username_3**: Actually, silicon oxide (as quartz or other silica minerals) is only that common in the uppermost part of the crust. There is hardly any silica, if at all, more than a few tens of km deep  
> **username_14**: Unless you are talking about normative oxide analysis, Michael, instead of quarts and other mineral forms. There is a lot of silicon bonded to oxygen that is counted as silicon dioxide.  
> **username_3**: And also MgO, CaO, Al2O3, FeO and whatever. Singling out SiO2 out of all oxides misses the point.  
> **username_13**: @Michael: No, it makes a point (though maybe you missed it :-)), which is that virtually all the oxygen is bound up in compounds.  Indeed, the only reason there's a significant amount of free oxygen in the atmosphere is photosynthesis.  
> **username_3**: @username_13 in compounds that are not necessarily silicon oxide. Therefore, there is no reason to single it out. Read my previous comment.  
> **username_14**: This is interesting and I'm going to spin off as a new question.  

---

