Electron Counting
Electron Counting - Related Videos
10:19
Using a Hemacytometer to Count Cells
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2023
Many biomedical experiments require manipulation of a known quantity of cells, in order to achieve accurate, reproducible, and statistically-relevant data. Therefore, learning how to count cells is a particularly essential technique for any successful biomedical scientist. The most common way to count cells is by using a hemacytometer - an instrument that bears two laser-etched grids, which aid in the enumeration of an aliquot cells under a simple light microscope. This data can then be used to...
05:47
Counting and Determining the Viability of Cultured Cells
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Cited by 19 •
2008
Determining the number of cells in culture is important in standardization of culture conditions and in performing accurate quantitation experiments. In this video, we demonstrate how cells are counted using a hemacytometer.
06:37
Counting Human Neural Stem Cells
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Cited by 14 •
2007
Knowledge of the exact number of viable cells is required for many tissue culture manipulations. This protocol describes how to differentiate between live and dead cells and quantify cells using a hemacytometer. Although it describes counting human neural stem/precursor cells (hNSPCs), it can be used for other cell types.
12:25
Counting Proteins in Single Cells with Addressable Droplet Microarrays
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Cited by 2 •
2018
Here we present addressable droplet microarrays (ADMs), a droplet array based method able to determine absolute protein abundance in single cells. We demonstrate the capability of ADMs to characterize the heterogeneity in expression of the tumor suppressor protein p53 in a human cancer cell line.
11:25
Knowing What Counts: Unbiased Stereology in the Non-human Primate Brain
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Cited by 22 •
2009
The anatomical organization of the primate brain can provide important insights into normal and pathological conditions in humans. Unbiased stereology is a method for accurately and efficiently estimating the total neuron number (or other cell type) in a given reference space1.
FAQs
Electron counting can be performed under different conventions, especially when oxidation states and formal charges are used versus when covalent bonds are assigned directly. These approaches organize the same bonding information differently, so totals should not be compared without identifying the convention. Stating the method makes analyses reproducible and prevents apparent disagreements in structures, ions, or complexes.
Atomic group numbers provide the starting valence-electron assignment, while formal charge adjusts the electron total associated with an atom. Covalent bonds and lone pairs then distribute those electrons in a molecular representation. This combination allows chemists to construct Lewis structures and check whether the resulting arrangement is consistent with the octet rule.
The octet rule and 18-electron rule apply to different common bonding contexts. Lewis-structure analysis often compares an atom's valence total with an octet, whereas many transition-metal complexes are examined against an 18-electron target. Selecting the relevant model helps interpret bonding and stability without treating one rule as universal.
To count electrons systematically, first identify the species and the convention being used. Assign valence electrons from group numbers, then account for formal charges or oxidation states as required by that convention. Include electrons represented by covalent bonds and lone pairs, total the result, and compare it with the appropriate bonding model.
For a Lewis structure, electron counting links numerical bookkeeping to placement of bonding and nonbonding electrons. The total is distributed among covalent bonds and lone pairs, after which the arrangement can be evaluated against the octet rule. This makes the technique useful for checking proposed structures rather than relying only on a drawn formula.
In organometallic chemistry, the count provides a common way to assess metal–ligand bonding and complex stability. Chemists can compare an electron total with the 18-electron rule, then use that analysis alongside oxidation states and bonding assignments when examining catalysts or likely reaction pathways. The result is an interpretive framework, not a substitute for stating the counting convention.