Predicting Bond Enthalpy Trends for Atom-Hydrogen Bonds

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Discussion Overview

The discussion revolves around identifying trends in bond enthalpy for atom-hydrogen bonds, specifically whether a predictable pattern exists across different elements. Participants are exploring theoretical aspects and empirical data related to bond dissociation energies calculated using Gaussian software.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if there is a period trend for bond enthalpy in atom-hydrogen bonds and seeks assistance in identifying such trends based on their calculations.
  • Another participant suggests that the original poster may have more insight into the trends since they performed the calculations, implying that their results could provide clarity.
  • A participant expresses uncertainty about the existence of a trend, noting that the calculated bond enthalpies do not seem to follow any clear pattern.
  • A later reply provides a reference table and states that for main group elements, bond dissociation energies (BDEs) generally decrease down the periodic table and increase across it, while for transition metals, M-H BDEs increase down the periodic table but lack a clear trend across the periodic table.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the existence of a clear trend in bond enthalpy for atom-hydrogen bonds, with some expressing uncertainty and others providing differing observations based on empirical data.

Contextual Notes

The discussion highlights potential limitations in the understanding of trends, including the dependence on specific definitions of bond enthalpy and the variability in trends observed for different groups of elements.

ReidMerrill
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Is there a period trend for bond enthalpy? Specifically Atom-Hydrogen bonds. Need to find a trend in predicting the bond enthalpy of several atom-hydrogen bonds I calculated using gaussian.

Any help would be appreciated, thanks!
 
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ReidMerrill said:
Need to find a trend in predicting the bond enthalpy of several atom-hydrogen bonds I calculated using gaussian.
If you calculated the bond enthalpies, wouldn't you be in a better position to tell us the trend, rather than us telling you?
 
TeethWhitener said:
If you calculated the bond enthalpies, wouldn't you be in a better position to tell us the trend, rather than us telling you?
I just wondered if there was supposed to be a trend since they don't appear to follow any pattern.
 
Try this table. https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf

For maingroup elements, E-H BDE's are fairly predictable: decrease down the periodic table, and increase across the periodic table.
For transition metals, M-H BDE's increase down the periodic table (1st < 2nd < 3rd). There's not really a clear trend across the periodic table.
 

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