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Related Concept Videos

Ionic Bonding and Electron Transfer02:48

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell. Compounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds: electrostatic forces of attraction between oppositely charged cations and anions.
Ionic Association01:28

Ionic Association

The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.
Ions and Ionic Charges03:27

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus — which contains the protons and neutrons of each atom and thus identifies the element — remains unchanged. Electrons, however, can be added to atoms by transfer from other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons to form electrically charged particles called ions.
Ionic Radii03:10

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it is smaller than the atom from which it is derived. For example, the covalent radius of an aluminum atom (1s22s22p63s23p1) is 118 pm, whereas the ionic radius of an Al3+ (1s22s22p6) is 68 pm. As electrons are removed from the outer valence shell, the remaining core electrons occupying smaller shells experience a greater effective nuclear...
Formation of Complex Ions03:45

Formation of Complex Ions

A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
Exceptions to the Octet Rule02:55

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:

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Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides
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Why are a(3) ions rarely observed?

Julia M Allen1, Alawee H Racine, Ashley M Berman

  • 1Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, USA.

Journal of the American Society for Mass Spectrometry
|November 1, 2008
PubMed
Summary
This summary is machine-generated.

The a(3) ion is not observed in tandem mass spectrometry (MS/MS) spectra of b(3) ions because it rapidly fragments further. This rapid fragmentation of the a(3) ion is due to its low energy and facile reaction pathway.

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Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

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Area of Science:

  • * Computational chemistry
  • * Mass spectrometry
  • * Proteomics

Background:

  • * Tandem mass spectrometry (MS/MS) is crucial for peptide sequencing.
  • * The fragmentation patterns of b(n) ions typically yield abundant a(n) ions.
  • * However, a(3) ions are notably absent in MS/MS spectra of b(3) ions.

Purpose of the Study:

  • * To investigate the reason for the absence of a(3) ions in b(3) ion MS/MS spectra.
  • * To elucidate the fragmentation mechanisms and energetics of b(3) and a(3) ions.

Main Methods:

  • * Experimental tandem mass spectrometry (MS/MS) analysis.
  • * Theoretical calculations of ion structures and transition states.
  • * Energy calculations for fragmentation pathways.

Main Results:

  • * Theoretical calculations confirm the conventional oxazolone structure for the b(3) ion.
  • * The a(3) ion is found to be energetically favorable compared to other a(n) ions.
  • * The transition state for a(3) --> b(2) fragmentation is lower in energy than other a(n) --> b(n-1) transition states.

Conclusions:

  • * The b(3) ion does fragment to form the a(3) ion.
  • * The a(3) ion possesses excess internal energy, leading to immediate secondary fragmentation.
  • * This rapid secondary fragmentation of the a(3) ion explains its absence in observed MS/MS spectra.