#atomic structure

[mineralsrocksandfossiltalks]

Wordplay Wednesday: Tetrahedral

Quartz has a tetrahedral structure. In fact, it has a perfect three-dimensional framework. That is why it is called a framework or tectosilicate like feldspar.

Here's a close-up of how these tetrahedra would interconnect. Each oxygen is shared between two tetrahedra.

Altogether, it would make this shape. And we see this shape with the naked eye.

[stone-cold-groove]

Your summer reading list: Atomic Spectra and Atomic Structure - 1944.

[materialsscienceandengineering]

Single-atom vacancies in atomically thin insulators created in ultra-high vacuum

Single photons have applications in quantum computation, information networks, and sensors, and these can be emitted by defects in the atomically thin insulator hexagonal boron nitride (hBN). Missing nitrogen atoms have been suggested to be the atomic structure responsible for this activity, but it is difficult to controllably remove them. A team at the Faculty of Physics of the University of Vienna has now shown that single atoms can be kicked out using a scanning transmission electron microscope under ultra-high vacuum. The results are published in the journal Small.

Transmission electron microscopy allows us to see the atomic structure of materials, and it is particularly well suited to directly reveal any defects in the lattice of the specimen, which may be detrimental or useful depending on the application. However, the energetic electron beam may also damage the structure, either due to elastic collisions or electronic excitations, or a combination of both. Furthermore, any gases left in the vacuum of the instrument can contribute to damage, whereby dissociated gas molecules can etch away atoms of the lattice. Until now, transmission electron microscopy measurements of hBN have been conducted at relatively poor vacuum conditions, leading to rapid damage. Due to this limitation, it has not been clear whether vacancies—single missing atoms—can be controllably created.

Read more.

[retrocgads]

UK 1985

[nemfrog]

Fig. 54. Copper and oxygen atoms superimposed on each other.  X rays and crystal structure. 1924.

Internet Archive

[gregorygalloway]

Robert Hofstadter (5 February 1915 – 17 November 1990)

[toyu-frey]

I’m busy writing a sci-fi book where due to space ships being treated as airplanes in the sense of ‘squeeze as many folks on board with as little room required as possible’, has lead to processors being used on board to generate food. How do the processors work? Idk.

I’m fooling around with the idea of using atom rearranging from space dust, only problem is, I can’t find the atomic particle of say, wheat, and other foodstuff. Are different plants/veggies/fruits (say, a apple vs a grape, or a apple vs rice) similar or different on the atomic level? Does the TYpE of plant the food grows from change the atomic stuff of the food, or just what the food grows on?

I’m gonna yeet this at NASA, cuz surely someone there has had a similar idea, or is knowledgeable on atomic stuff in general to know what a apple or a grain of wheat is on the atomic level. And science side of tumblr, just for the heck of it.

#official-NASA

#science-side-of-tumblr

[a-level-study-bunny]

MASS SPECTROMETRY (PART 1)

Mass spectrometry is a highly useful form of analysis, with the most commonly used type of mass spectrometry being time of flight (ToF) spectrometry. ToF spectrometry has multiple uses such as:

Finding out the relative atomic mass of an element by finding the mass and abundance of isotopes within the element

Finding out the relative molecular mass of a molecule

THE STAGES

There are multiple steps involved in the process and we need to know all of them (I know - I wish we didn't have to either but the AQA spec says so...)

Ionisation

Acceleration

Ion drift

Detection

1) IONISATION

There are actually two types of ionisation that we need to know that can happen in a ToF spectrometer. Electron impact ionisation (a.k.a. electron ionisation) and electrospray ionisation.

Electron impact ionisation (a.k.a. electron ionisation)

This process is done by first being vaporised and then bombarded with electrons that are fired from an 'electron gun' (i.e. a hot wire filament with a current that runs through it and emits electrons). This typically results in an electron being knocked off of each sample particle to form a 1+ ion. These 1+ ions are then attracted to a plate with a negative charge (this is where they're accelerated!) - However, this is a rather harsh form of ionisation and frequently results in fragmentation of the molecular ion (this results in fragments being picked up on the mass spectrum) - This is good to know, but also not actually in the specification! :)

Electrospray ionisation (this is a soft ionisation technique)

To start, the sample is mixed with a volatile solvent. This is then pushed through a hypodermic needle at high velocity. The needle has a high voltage held through it to shock the sample particles as they pass through. This results in a cloud of positively charged 1+ ions (they lose an electron because of the high voltage shock!) The ions are then accelerated by a negative plate.

2) ACCELERATION

The positive ions are accelerated using an electric field. This results in them all having the same kinetic energy. (Super important for the next stage!)

3) ION DRIFT

The +1 ions travel through the middle of a negatively charged plate (through a hole) into a tube. This is the stage where the ions drift through a field with no charge. The thing that differentiates these ions is their mass/charge ratio. The higher the mass/charge ratio, the heavier the ion, the slower it goes (and vice versa). This means they hit the detector at different times (thus showing the abundance - but I'll explain that in a moment!)

4) DETECTION

The 1+ ions hit a negatively charged plate. This contact causes the ions to lose their charge as they collect an electron from the plate. This results in a movement of electrons, which produces an electric current that we can measure. The more electrons that hit the plate at once, the larger the current. This then translates on the mass spectrum as a larger spike.

If you've made it this far, well done!! You deserve a cookie (or something... I don't have one for you, but you deserve one!!)

Now that you've looked at all of that, it's time to look at the results! But since this post is already rather long, I will be making another post to cover that! (Sorry!)

Useful AQA resources:

https://filestore.aqa.org.uk/resources/chemistry/AQA-7404-7405-TN-MASS-SPECTROMETRY.PDF - This has pictures etc and is official AQA material :D