What is Molecular structure: Definition and 21 Discussions

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge.
In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions.
In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. This violates the definition that a molecule contain two or more atoms, since the noble gases are individual atoms.A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (two hydrogen atoms and one oxygen atom; H2O).
Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not considered single molecules.Molecules as components of matter are common. They also make up most of the oceans and atmosphere. Most organic substances are molecules. The substances of life are molecules, e.g. proteins, the amino acids they are made of, the nucleic acids (DNA & RNA), sugars, carbohydrates, fats, and vitamins. The nutrient minerals ordinarily are not molecules, e.g. iron sulfate.
However, the majority of familiar solid substances on Earth are not made of molecules. These include all of the minerals that make up the substance of the Earth, soil, dirt, sand, clay, pebbles, rocks, boulders, bedrock, the molten interior, and the core of the Earth. All of these contain many chemical bonds, but are not made of identifiable molecules.
No typical molecule can be defined for salts nor for covalent crystals, although these are often composed of repeating unit cells that extend either in a plane, e.g. graphene; or three-dimensionally e.g. diamond, quartz, sodium chloride. The theme of repeated unit-cellular-structure also holds for most metals which are condensed phases with metallic bonding. Thus solid metals are not made of molecules.
In glasses, which are solids that exist in a vitreous disordered state, the atoms are held together by chemical bonds with no presence of any definable molecule, nor any of the regularity of repeating unit-cellular-structure that characterizes salts, covalent crystals, and metals.

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  1. Z

    Chemistry Why doesn't the formula of chlorine nitrate contain a positive charge?

    Looking up on the internet the structure is My question is why (or, better, how) do we know that there is that positive charge on the nitrogen? Wouldn't the overall molecule have a positive charge in it? Then why is this not denoted in the formula ##ClONO_2##?
  2. S

    Hexagon Patterns in Chemical/Molecular Makeup

    Are physical atoms really arranged in hexagon patterns, or is that some sort of way to represent them for illustrations in textbooks and in science articles? (i.e. atoms aren't actually arranged in any hexagon pattern)
  3. J

    Chemistry Why Does IF5 Exhibit a Square Pyramidal Shape Despite Exceeding the Octet Rule?

    I thought it was trigonal bipyramidal, with iodine forming 5 bonds with 5 fluorine atoms. Actually, iodine has another lone electron pair, making it square planar. Is there a reason why iodine has another lone pair when it has already exceeded the octet rule? And how would I predict how many...
  4. sams

    Calculating the Molecular Orbitals of a Molecular State

    I am performing ab initio calculations on a heteronuclear diatomic compound using the MRCI method on the MOLPRO quantum chemistry package. I obtained the molecular states of the compound but I was wondering how to find the molecular orbital configuration of each electronic state in addition to...
  5. M

    I What happens in the molecular structure of a liquid (imcompressible)?

    Suppose you have a liquid with high potential energy at a height [H] in a first moment. In a second moment, the liquid loses its potential energy (that is converted into kinetic energy) and fall in a cylinder at height [h] .IF the liquid is incompressible what happens with the molecules in the...
  6. JTC

    B Tearing Tape: Understanding the Differences in Fracture Behavior

    (If this is posted in the wrong area, please feel free to move it.) If I take Scotch tape (using the product name), pull out a long strand and then, beginning at the free end, tear it down along its length (to get two strips of the same length, but thinner), the "fracture" (if I may call it...
  7. sams

    How Are Coefficients of Secular Equations in LCAO Evaluated?

    Dear Everyone, I would like to ask a question regarding the evaluation of the coefficients in Linear Combination of Atomic Orbitals (LCAO). In Molecular Quantum Mechanics book authored by Peter Atkins and Ronald Friedman (Fourth Edition ISBN 0199274983), we are trying to calculate the...
  8. B

    Chemistry "Simple molecular structure do not conduct electricity" H2O?

    Homework Statement Book says "Substances with a simple molecular structure do not conduct electricity. This is because they do not have any free electrons or an overall electric charge". Homework EquationsThe Attempt at a Solution I think the statement is a generalization because water is a...
  9. skulliam4

    Quantum Tunnel Macro-Scale Structure Disassembly

    I have done my research and understand why quantum tunneling happens and I fully understand that there is no point at which the particle examined ever actually intersects with the barrier. The only part at which my knowledge feels fuzzy is at the mathematic equations. If a large object, such as...
  10. T

    Chemistry Molecular Structure: Thorium & Rubidium; Thorium & Phosphour

    Homework Statement Got a homework question for what kind of molecular structure you would get by combining these to metals: Thorium and rubidium, thorium and phosphour. Got to draw the Lewis diagrams and VSEPR model for these molecular structures, and predict the geometry - bond angles - bond...
  11. M

    Effect of Cooling on Molecular Structure

    I am interested in knowing whether what changes would happen at the molecular and atomic level, to a material subjected to Cooling. 1. Does the minimum temperature that can be achieved has limit? 2. Is it Zero Kelvin? 3. If so, is it a global standard for minimum temperature for any material...
  12. A

    Why Do SO2 and XeO4 Form Different Types of Bonds?

    The S molecule of SO2 forms a double bond with one O and dative covalent bond with another O Meanwhile,XeO4 is a molecule which Xe forms a double bond with each O I have a question here Why doesn't that S forms 2 double bonds with O to extend its octet structure? Similarly,why doesn't that...
  13. M

    Can sodium chloride be categorised as a giant molecular structure

    I was attempting this question where I had to say which, out of graphite, diamond and sodium chloride represent a giant molecular structure? The answer is only the first two. Why is the latter excluded?
  14. edpell

    Can I simulate molecular structures without being a chemist?

    I am not a chemist. I have a molecular structure question. Is it possible to bind two positively charged molecules together by having two electrons bounce up and down in the space between them? M1+ e e M2+ imagine the e, electrons oscillating up and down. Either in sync and 180...
  15. ~christina~

    Chemistry Molecular structure and analysis method

    Homework Statement \Delta9-Tetrahydrocannabinol (THC) is the primary psychoactive constituent of marijuana. Its metabolites include 11-hydroxy- \Delta9-THC (11-OH-THC) and 11-nor-9-carboxy- \Delta9-THC (THC-COOH). 1)Write down the molecular structure of these three compounds. 2)Develop an...
  16. E

    Chemistry H NMR Spectrum - Molecular Structure

    Homework Statement Give the structure of C8H8O3.Homework Equations IR tells us that there is an OH group and a C=O group Degree of saturation = 5 --> Benzene ring + C=O H NMR spectrum shows: Peak at ~7.8ppm integrating for 1H and is a doublet Peak at ~7.45ppm integrating for 1H and is a...
  17. A

    Chemistry Features in the molecular structure of a compound that affect solubility mp,bp.

    Hi guys, I need some help with this question. What features in the molecular structure of a compound affect its solubility and its melting and boiling points. I need to answer this question with several examples and include structural diagrams. Please help
  18. H

    Potential Energy of Ions in a Molecular Structure

    okay here's the equation: In a certain molecular structure, the total energy E between two ions is given by E= (-5.6/r) + 10e^(-r/3) where r is the distance seperating the nuclei. now i already sketched the graph but i don't know how to find the domain of E, or...
  19. B

    Exploring Molecular Structure of Silicon & Carbon Dioxide

    Hey all Why does Silicon Dioxide have a Giant molecular structure, while Carbon dioxide is made of simple molecules? They both have 4 electrons on their valence shells, so why wouldn't Silicon Dioxide be a simple linear molecule? (gaseous).
  20. B

    Drawing Lewis Dot Diagrams: Rules Beyond the Octet Rule

    What are the rules for drawing Lewis dot diagrams, besides the 1) Carbon usually has a full octet 2) Some atoms become electron deficient, others electron sufficient 3) The Duet Rule 4) Link OH if written in the formula What the "other" rules? For example, i try to draw glucose...
  21. C

    Question about molecular structure (chemistry related)

    My professor wants the class to put some different chemical formulas in molecular structure while following the HONC Rule. He gave us six different chemical forumals to convert and I have finished five of them correctly; however, there is still one giving me trouble. Here is the given formula...