Nature of Magma

[popcornfrenzy]

I just want to ask how oxygen, silicon, aluminum, potassium, calcium, etc., basically the liquid portion of magma, how are they in liquid form?

In our textbook, it was mentioned that the melt consists of mobile ions of these elements so does it mean the liquid part is a congregate of ions in the form of ionic liquid? 

The part that got me confused is with the characteristic of oxygen because it only exists as a liquid in -183 ^oC, presumably at lower temperatures, while the asthenosphere is around 1300 ^oC which makes me think that it should be in a gaseous form. Why is it a liquid along with the other elements I mentioned? 

[studiot]

2 hours ago, popcornfrenzy said:

I just want to ask how oxygen, silicon, aluminum, potassium, calcium, etc., basically the liquid portion of magma, how are they in liquid form?

In our textbook, it was mentioned that the melt consists of mobile ions of these elements so does it mean the liquid part is a congregate of ions in the form of ionic liquid? 

The part that got me confused is with the characteristic of oxygen because it only exists as a liquid in -183 ^oC, presumably at lower temperatures, while the asthenosphere is around 1300 ^oC which makes me think that it should be in a gaseous form. Why is it a liquid along with the other elements I mentioned? 

Good question, keep them coming. +1

First it is worth noting that rocks in general are not molten at the depths concerned and that rocks are made of minerals which are ionic crystals when solid.
When these rocks melt they are called magmas.
They melt for two reasons, heat and pressure release.
Heat is generated as rocks are drawn downwards from above (subduction) or simply buried by earth movements and also rises from yet deeper layers.
This rising heat is not evenly distributed but concentrates in vertical convection cells (plumes).
However the deeper the rocks are the greater the pressure on them and so they cannot necessarily melt (turn into a liquid and flow) even if the temperature is above their melting point.
The extra heat from below is one way to generate the molten state that is magma, and why volcanoes etc occur in some locations and not others.
When such rock is moved upwards by earth movements the pressure is lowered or released and more rock melts to magma.
When the melt occurs cations (+ve) and anions (-ve) are formed.
Oxygen is often combined with elements such as silicon to form complex anions (SiO₄)^- which are stable at such temperatures and pressures.
Water is also available and involved.

Britannica has a good not too technical description. Note the opening statement.

Quote

Nature of magmas

Magmas are chemically complex fluid systems that differ in many ways from ordinary solutions, in which water is the solvent and the dominant constituent.

https://www.britannica.com/science/igneous-rock/Nature-of-magmas

Does this help ?

[exchemist]

3 hours ago, popcornfrenzy said:

I just want to ask how oxygen, silicon, aluminum, potassium, calcium, etc., basically the liquid portion of magma, how are they in liquid form?

In our textbook, it was mentioned that the melt consists of mobile ions of these elements so does it mean the liquid part is a congregate of ions in the form of ionic liquid? 

The part that got me confused is with the characteristic of oxygen because it only exists as a liquid in -183 ^oC, presumably at lower temperatures, while the asthenosphere is around 1300 ^oC which makes me think that it should be in a gaseous form. Why is it a liquid along with the other elements I mentioned? 

The first point is that all these elements are present in the form of compounds, in which their atoms are chemically bound to other atoms, whether by ionic or covalent bonding. The boiling point of oxygen (O2) is therefore not relevant, since free molecular oxygen is not what is being referred to.

As @studiot says, oxygen is mostly present in magma as various kinds of silicate. The chemistry of silicates is very complex, but is all based around variants of the tetrahedral SiO4 unit, sometimes free but more often joined to others by shared vertices, to form chains, sheets or 3D arrays. These units are covalently bonded but tend to have a net -ve charge, thereby forming a family of silicate anions (SiO4⁴⁻, Si2O7⁶⁻, and so on) that can complement the metals you list, since they will be present in the form of cations. (You may be familiar with other complex anions such as carbonate CaCO3²⁻,  sulphate SO4²⁻ etc, which also have covalent bonding internally but a net -ve charge overall. Silicates are like that.) 

However it is worth noting that pure silica itself, SiO4, in which SiO4 units form a 3D array, has no ions. When this melts, it requires some of the covalent bonds to break, temporarily, and reform, allowing the units to slide past one another. You get silica in most magmas, along with various silicates.

 

[popcornfrenzy]

Thanks to both of you for the answers I can finally get a clearer picture on how these elements behave as a compound in the magma, I actually thought oxygen exists here as an ion along with the others that I mentioned. Good thing it was cleared up.

[exchemist]

7 hours ago, popcornfrenzy said:

Thanks to both of you for the answers I can finally get a clearer picture on how these elements behave as a compound in the magma, I actually thought oxygen exists here as an ion along with the others that I mentioned. Good thing it was cleared up.

Glad it helped. By the way I see I made a typo in the formula for silica, which should be SiO2, not SiO4. (Although the units are SiO4 tetrahedra, by the time they share all their "O" vertices with neighbouring ones, the overall ratio of O:Si becomes 2:1.) 

[popcornfrenzy]

On 4/23/2021 at 4:43 PM, exchemist said:

Glad it helped. By the way I see I made a typo in the formula for silica, which should be SiO2, not SiO4. (Although the units are SiO4 tetrahedra, by the time they share all their "O" vertices with neighbouring ones, the overall ratio of O:Si becomes 2:1.) 

Oh I'll take note of that isn't the SiO2 the empirical formula or did I get that wrong?

[exchemist]

7 hours ago, popcornfrenzy said:

Oh I'll take note of that isn't the SiO2 the empirical formula or did I get that wrong?

You're right, it's the empirical formula.

Silica (quartz) is a covalent giant structure. As such, there is no molecular formula, since there are no discrete molecules in the structure. You could almost say that an entire crystal is in effect a single "molecule! So for giant structures, the empirical formula is what we use. 

Here is a picture, in which you can see the SiO4 tetrahedra sharing the O atoms at their vertices with their neighbours: