100 Nano-Stories: Silica vs. Silicon + Oxidation of Silica!

Episode #80: All About Silica!

Carlos Manuel Jarquín Sánchez
4 min readApr 25, 2021

Preface! ✨

It’s your favorite material science & nanotechnology enthusiast! Today, I will cover more about the silica atom and how to calculate the oxidation state (to explain why silicon dioxide is such a great molecule for silica aerogels.)

For a brief review on what Oxidation is, I recommend reading the article below:

TL;DR → Oxidation! 🔑

  • Oxidation means the number of electrons of an atom in a chemical compound that was lost or gained via the process known as oxidization. This number is known as the Oxidation Number!
  • Oxidation numbers may look like this: (-2, +2, +4)
  • If an atom has a negative number, it means that the element has gained electrons from another element.
  • If the element has a positive number, it means that the element has lost electrons from another element.
  • To calculate the oxidation state of any organic molecule/compound, you find the number of valence electrons of the main element minus the valence electrons from other atoms attached to that main element (in the diagram given).
  • Valence Electrons are the electrons in the outer shell/last row of an atom.

Now that the main concepts are out of the way, let’s first resolve the remaining difference between Silica and Silicon!

Silica v. Silicon Explained! 💡

Similarities and Differences! 🔑

Right off the bat, Silicon is an element on The Periodic Table of Elements.

Silicon Dioxide/Silica is made of Silicon and Oxygen Atoms (the main compound is SiO2.)

Silica has a higher melting & boiling point than silica because there are more covalent bonds that hold the molecule together than in the silicon atom. The more covalent bonds, the temperature must go higher to break the intramolecular bonds.

Melting Point of Silicon → 1414 °C (2577.2 °F)

Melting Point of Silica → 1713 °C (3115.4°F)

Boiling Point of Silicon → 3265°C (5909°F)

Boiling Point of Silica → 2,230°C (4,046°F)

Oxidation of Silica! 💡

In Silicon Dioxide/Silica, the oxidation numbers will all add up to zero, since silica is a stable & neutral compound.

But to solve the oxidation of silica, this is how the silica compound looks like:

The main element in the diagram is the silicon atom, which has two oxygen atoms that are double-bonded to the silicon atom.

The oxidation number of oxygen is -2, since the number of valence electrons in the outer shell of oxygen is 6, and you need to add 2 more electrons to “satisfy” the outer shell of oxygen.

The normal oxidation number of the silicon atom is 0, but that doesn’t work because we need the oxidation numbers in the compound to equal 0.

So what we can do to calculate the oxidation number of silicon in silica is by multiplying the oxidation number of both oxygen atoms (-2 x 2 = -4). -4 is the oxidation number for both oxygen atoms, which gives us this conclusion:

  • To have the oxidation numbers of silicon dioxide equal to zero, the silicon atom must have an oxidation number of +4.
  • A -4oxidation number from both oxygen atoms and a “+4” oxidation number from the silicon atom equal an overall oxidation number of zero!

Closing Thoughts! 💭

This should now give us a better explanation of why silicon dioxide/silica is such a valuable compound when making silica aerogels, and why it is used for many applications (such as aerogel.)

I will cover the last sections of optical properties of silica aerogel in the final episodes (Episodes #81-#85) before returning to more of the combination of chemistry & mathematics in aerogels before announcing an idea that I would like to explore more!

See you soon for optical properties in silica aerogels for solar applications! ✌🏽

Vocabulary! 📓

OxidationThe number of electrons of an atom in a chemical compound that was lost or gained via the process known as oxidization. This number is known as the Oxidation Number!

Covalent BondsThey are chemically bonded because the electrons are being shared evenly! Covalent bonds form between two nonmetals! Sharing is caring! 😄

Valence ElectronsElectrons in the outer shell/last row of an atom.

Silicon Dioxide/Silica A compound comprised of Silicon and Oxygen Atoms (the main compound is SiO2.)

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© 2021 by Carlos Manuel Jarquin Sanchez. All Rights Reserved.

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