Charge Size Ratio
Charge Size Ratio - Related Videos
02:54
Trends in Lattice Energy: Ion Size and Charge
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2020
An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure of the strength of this attraction. The lattice energy (ΔHlattice) of an ionic compound is defined as the energy required to separate one mole of the solid into its component gaseous ions. For the ionic solid sodium chloride, the lattice energy is the enthalpy change of the process: Conventions Here, the convention is used where the ionic...
09:12
Electric Charge in a Magnetic Field
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2023
Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA This experiment duplicates J.J. Thomson's famous experiment at the end of the 19th century, in which he measured the charge-to-mass ratio of the electron. In combination with Robert A. Millikan's oil-drop experiment a few years later that produced a value for the charge of the electron, the experiments enabled scientists to find, for the first time, both the mass and the charge of the electron, which are key...
02:42
Formal Charges
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2020
In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to help predict the most appropriate Lewis structure when more than one reasonable structure exists. Calculating Formal Charge The formal charge of an atom in a molecule is the hypothetical charge the atom would have if the electrons in the bonds are evenly distributed between the atoms. Alternatively, formal charge results when from the number...
03:27
Ions and Ionic Charges
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2020
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. When...
03:08
Atomic Radii and Effective Nuclear Charge
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2020
The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number and distribution of electrons in their valence shells. Going across a period from left to right, a proton is added to the nucleus and an electron to the valence shell with each successive element. Going down the elements in a group, the number of electrons in the valence shell remains constant, but the principal quantum number increases by...
FAQs
Migration in an electric field reflects a balance between electrical driving force and resistance from the surrounding medium. Net charge affects how strongly a molecule responds to the field, whereas physical size contributes to friction and slows movement. Consequently, molecules with different charge and size combinations may migrate at similar rates, so charge size ratio must be interpreted alongside shape and medium resistance.
Shape changes how a molecule experiences resistance as it moves through the electrophoresis medium. Two molecules with comparable charge and overall size can therefore show different migration behavior if their shapes create different hydrodynamic effects. Field strength and the medium itself also influence movement. These variables explain why migration patterns cannot be assigned to charge alone when comparing biological samples.
In SDS-PAGE, detergent binds to proteins and produces a similar negative charge-to-mass relationship among them. This reduces the influence of native charge differences on migration, allowing size-related friction to become the primary basis for separation. The resulting pattern supports protein characterization because differences in migration are interpreted mainly in relation to protein molecular size.
A useful comparison requires examining migration under a defined electric field and within a specified medium, then comparing the rates or positions observed for the samples. Interpretation should account for charge, size, shape, field strength, and medium resistance rather than treating migration distance as a direct size measurement in every format. SDS-PAGE provides a more size-focused comparison for proteins.
Charge size ratio is useful when researchers need to relate electrophoretic behavior to molecular properties. It supports protein characterization, nucleic acid analysis, and comparisons between biological samples by helping explain why molecules move differently through an electric field. The concept is especially valuable when interpreting electrophoretic patterns and deciding whether charge, size, or both may contribute to an observed difference.
A migration difference may reflect several factors besides size, including net electrical charge, molecular shape, field strength, and resistance from the electrophoresis medium. Larger molecules generally experience more friction, but greater charge can promote faster movement. Therefore, electrophoretic patterns require contextual interpretation, with SDS-PAGE offering a format in which protein separation is primarily associated with molecular size.