In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid.

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Grocery store crystalline citric acid

Which type of citric acid crystalline powder do they sell in grocery stores? Is the concentration of citric acid in the crystals 100%?Is it anhydrous or a monohydrate?
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Represent bonds spanning a unit cell boundary plane

Is there a chemical input format that is- Supported by Open Babel (and hence supports visualization in avogadro??) Can represent a bond connecting an atom to its partner in a neighbouring unit cell, ...
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40 views

What happens when ice melts?

What happens when ice melts? I have this question, with two possible answers: regularly arranged molecules change into irregularly arranged molecules water molecules become less densely packed ...
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how to determine timescale with characterization methods?

There are as classified in the Atkins textbook 4 different timescales on material characterization: a)Time during which a quantum of radiation or a particle can interact with a molecule. b)Lifetime of ...
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Dihedral angle of gaseous and crystalline HOOH

Why does hydrogen peroxide exhibit a dihedral angle of 111.5 degrees in the gaseous state? And a dihedral angle of 90.2 degrees in the crystalline phase? I know that in general, there is likely to ...
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Is there a systematic way to determine the expected cubic structure of metals?

I've noticed that some groups of metals with similar properties tend to belong to the same cubic structure group, such as $\text{FCC, BCC, or HCP}$. What is a good explanation as to why these metals ...
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How do people check the type of defect in a crystal?

There are many types of defects like Vacancy Interstitial Schottky Frenkel Non-Stoichiometric Alien Impurities But given a sample, how do scientists know which kind of defect is present in it ...
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30 views

What is the length of a unit cell of CuCl assuming that it is fcc?

The density of CuCl is given - x gm/cmm The crystal structure is assumed to be fcc. My teacher is claiming the we can apply the formula $$\rho=\frac{Z * M}{a^3 * N_0}$$ And he took M = 35.5+63.5gm = ...
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39 views

Structure of diamond

"diamond structure. Every carbon atom is bonded to four other carbon atoms forming a three-dimensional lattice of chair conformations." SENTENCE FROM A BOOK What does this mean? Where I am struck ...
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What are Lattice Points

What are lattice points exactly? And Also How many Lattice Points are there in each of the Unit Cells?
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298 views

What are these crystals on my champagne cork?

I opened up a bottle of champagne that was left in a wine cooler for approx. 8 years. To my astonishment there were small crystals at the underside of the cork. The crystals are colorless, odorless ...
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Crystal structure in function of pressure

If you were to investigate crystal structure changes as a function of pressure, which metals would you study first? Last? Why?
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Elementar cell of Y2O3

I think this picture from wikipedia is wrong because I count: \begin{align} \left. \begin{array}{ccccr} 1&×&1 &= &\ce{1~Y} \\ 6&×&\frac{1}{8} &= &\ce{\frac{3}{4}O} ...
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Is BCl₅ possible?

Is $\ce{BCl5}$ possible? I saw it in book. As far as we can see there is no way to get 5 chlorine atoms with boron.
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If salt crystals make a cube shape, what is this 'X' marking?

I am an amateur, with very little professional chemistry knowledge. I was doing a demonstration / experiment with my 6 year old child. We took very warm normal tap water, and dissolved into it a ...
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52 views

Chemical bonding - lattice energy

Question: Why is ionic lattice energy inversely proportional to the radius of the atom? Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, ...
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Polymer Crystallinity

See the following question: I think the answer is A because of the hydrogen bond in the side group, thus the degree of secondary bonding between parallel chain segments is higher. Is my thinking ...
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68 views

How does the crystal know where to stop stacking the unit cells?

I tried to make different crystals in the cubic system by stacking cubes in a 3d software. However I need to tell the software where to skip rows or stop stacking the unit cells in a specific ...
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How do we know the size of atoms in body centered cubic system?

I'm told that in the normal cubic system there are $\frac18$ of an atom at each corner and these atoms' radius are such that $a = 2r$ ($a$ is the lattice constant, $r$ radius of an atom). In bbc ...
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Are metallic/ionic bonds weaker than covalent bonds? I was taught the opposite. Now I'm confused

In mineralogy class, I was taught that metallic and ionic bonds are weaker than covalent bonds and that's why quartz and diamond have such a high hardness value. However, in organic chemistry class, I ...
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Why do NaHCO₃ and KHCO₃ have different crystal structures?

Why do $\ce{NaHCO3}$ and $\ce{KHCO3}$ have different crystal structures? We had this in a test today and this got me stumped... My questions are: Do $\ce{NaHCO3}$ and $\ce{KHCO3}$ possess ...
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62 views

Bonding, multiplicity and quantum chemistry for FeP$_2$

I'm trying to do some quantum chemical calculations for the linear molecule FeP$_2$ in the gas phase as well as its crystal (orthorhombic symmetry like here). I am lead to believe that in both cases ...
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28 views

How to determine mineral properties based on chemical formula?

I need to learn a bunch of minerals and their properties. What I want is some sort of rule which helps me deduce color, crystal system, luster etc. I know that different kind of ions give specific ...
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117 views

How to memorize 7 crystal systems?

Is there any trick to memorize the angles and sides of 7 crystal systems of crystalline solids? 1. Cubic 2. Tetragonal 3. Orthorhombic 4. Monoclinic 5. Hexagonal 6. Rhombohedral or Trigonal 7. ...
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What is the minimum distance of Rubidium and Iod ions in a centered cube?

I have a problem to visualize the following assignment: What is the minimum distance between $\ce{Rb^+}$ and $\ce{I^-}$ ions if radius of $\ce{Rb^+}$ is ${1.49\cdot10^{-10}}~\mathrm{m}$ and radius ...
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How many Ga atoms are connected to one As atom in solid state Gallium arsenide

Let's start straight away. In this book on page 4 Gallium arsenide's bond structure is shown like this: $As$ is shown making $5$ covalent bonds. Recently I came across this book. The bond structure ...
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Hexagonal unit cells

I know 3 types of unit cells, the simple cubic, the body centered and the face centered. But what is a hexagonal unit cell, and why does it have a hexagon base while others are all cut into a cubic? ...
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Why is there one octahedral and two tetrahedral positions for every anion in a close packed structure?

I'm reading about ionic crystal structures with planes of close-packed anions and the interstitial sites for cations. There are two types of interstitial sites: tetrahedral and octahedral. That makes ...
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Why are cations ordinarily smaller than anions?

I'm reading on ionic crystal structures and am confused by this from my textbook: Because the metallic elements give up electrons when ionized, cations are ordinarily smaller than anions I ...
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154 views

Is a diamond a single molecule?

Assuming a perfect diamond with no impurities. Would this diamond considered to be a single large molecule? Browsing the interweb I found several opinions about this but did not find a clear Yes or ...
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172 views

is there any mnemonic for the AXE method?

Is there any mnemonic that helps remembering the names of the different geometries (Shapes) that we obtain from applying the AXE method ?
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Is it possible to cut yourself on pyrite?

I am planning an RPG adventure where the characters might end up getting a large cubic lump of "gold", which in reality, as you might have guessed, is in fact pyrite. I also wanted to plan for the ...
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Why does ZnO turn yellow when it is hot?

Why does ZnO's color become yellow when it is hot? I have read that it is because of physical properties, but I need a more elaborate explanation.
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How do you determine a chemical formula given the molecule's crystal structure?

How do you determine the chemical formula of a compound given its crystal structure?
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How to calculate lattice parameter only using planes and d spacing

I am trying to find lattice parameter of a hexagonal crystal, usually I use cellcalc for calculating lattice parameter of a crystal structure. In that software it asks only two queries, one is details ...
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Rapidly cooling Aluminum vapour to solid state?

What sort of a microstructure would you get on bubbling Aluminium vapors through a large tank of Helium?Would it be a glassy microstructure and/or would you get nano-powders? and/or a new crystal ...
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Bond Lengths in FCC, BCC and HCP Structures

I was wondering what the crystal structures of FCC, BCC and HCP actually look like, and where atoms are placed in their configuration? Specifically I'm looking at elemental nickel, iron and cobalt ...
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What's the difference between alpha-glucose and beta-glucose?

What's the difference between $\alpha$-D-glucose and $\beta$-D-glucose? Are they isoforms? Or do they differ in their elemental composition?
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What's up with SiO2 being tetrahedral?

If silicon dioxide tends to form a crystal lattice with four Os around a central S, why isn't the molecular formula $\ce{SiO4}$ then? I'm confused why it's unique in that its molecular formula doesn't ...
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123 views

Wasn't Rutherford's assumption of gold foil to be made of single layer wrong?

My teacher taught about Rutherford's gold foil experiment today. Sir said that, Rutherford used gold foil of thickness $10^{-7}$ m and concluded atom to be of size $10^{-10}$ m. Sir also said that ...
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What is the edge of a diamond like?

The chemical structure of a diamond is defined as an endless lattice in which each carbon atom is covalently bonded to four other carbon atoms situated at the four ends of a tetrahedron. But of ...
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What conditions to use to crystallise Equine Myoglobin?

What are the crystallisation conditions for Equine Myoglobin? I've tried repeating some from the PDB but no success.
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What does the Sm5Ge4 orthorhombic structure look like?

I see tons of papers referencing this structure but none show what it looks like.
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Why polymorphs form?

We always hear about the different arrangements of molecules that lead to the formation of polymorphs, my question here is why would a polymorph form in the first place? The material was given enough ...
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Relating a compound's radii and unit cell dimensions

We're asked often to calculate the density of a crystal, and there is a known formula for that related to the unit cell volume. Now, for simple geometric structures such as the bcc structure (and ...
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222 views

How do point defects in a crystal relate to Entropy?

I am interested in Non-Stoichiometry and how it relates to crystal structures; In particular I wish to learn about surfaces of metal oxides. I am aware that point defects in such crystals are a result ...
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How to calculate crystal field stabilisation energy?

How to calculate it? I know that it depends on the coordination compound and the number of electrons present in t2g and eg orbitals and the final answer is expressed in terms of crystal field ...
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Stoichiometric defects in ionic crystal?

The stoichiometric defects (Schottky and Frenkel defects) in ionic crystals are formed due to irregularities in ionic arrangement all the while maintaining the stoichiometry and electric neutrality. ...
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Liquid crystal current flow

In a liquid crystal cell used for LCD the conductive substrates, usually made of ITO, are in contact with the liquid crystal. The question is: when a voltage is applied to the electrodes to reorient ...
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Is it possible to save an insoluble snowflake?

In The Big Bang Theory Season 3 Episode 1 "The Electric Can Opener Fluctuation" Leonard gives Penny a snowflake that will never melt. He said some type of chemical gas name when he try to explain, ...