Group 15 Exceptions
Group 15 Exceptions - Related Videos
02:55
Exceptions to the Octet Rule
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2020
Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories: Odd-electron molecules have an odd number of valence electrons and therefore have an unpaired electron. Electron-deficient molecules have a central atom with fewer electrons than needed for a noble gas configuration. Hypervalent molecules have a central atom that has more electrons than needed for a noble gas configuration. Odd-electron...
01:16
Other Nuclides: 31P, 19F, 15N NMR
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2024
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research. While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
08:44
Microplot Design and Plant and Soil Sample Preparation for 15Nitrogen Analysis
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Cited by 2 •
2020
A microplot design for 15N tracer research is described to accommodate multiple in-season plant and soil sampling events. Soil and plant sample collection and processing procedures, including grinding and weighing protocols, for 15N analysis are put forth.
09:25
NMR 15N Relaxation Experiments for the Investigation of Picosecond to Nanoseconds Structural Dynamics of Proteins
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2024
Nuclear magnetic resonance (NMR) spectroscopy can characterize structural protein dynamics in a residue-specific manner. We provide a hands-on protocol for recording NMR 15N R1 and R2 relaxation and {1H}-15N heteronuclear Overhauser effect (hetNOE) experiments, sensitive to the picoseconds to nanoseconds timescale.
08:09
15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale
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Cited by 11 •
2021
Here, a detailed description of the protocol implemented in the laboratory for acquisition and analysis of 15N relaxation dispersion profiles by solution NMR spectroscopy is provided.
FAQs
Down Group 15, increasing atomic size changes how effectively orbitals overlap during bonding. Nitrogen can achieve strong orbital overlap, which supports stable multiple bonds, whereas larger atoms generally show different bonding behavior. These size and overlap differences help explain why compounds of heavier elements may not follow the bonding patterns expected from nitrogen.
Nitrogen commonly reaches a maximum covalency of four and forms strong multiple bonds. The heavier Group 15 elements can expand their valence shells, allowing bonding arrangements that are less accessible to nitrogen. This contrast affects molecular structure and compound stability, so nitrogen compounds should not be interpreted as simple models for every heavier group member.
The inert-pair effect makes the outer electron pair less available for bonding in the heavier Group 15 elements. As a result, lower oxidation states become increasingly favored, particularly toward bismuth. This trend changes the relative stability of compounds and helps explain why oxidation-state behavior down the group departs from a straightforward periodic prediction.
Predictions should account for atomic size, electronegativity, orbital overlap, bond strength, and the inert-pair effect together. No single factor explains every exception. Their combined influence can alter molecular structure, reactivity, acidity, redox chemistry, and stability, allowing apparently irregular behavior to be interpreted through connected physical and electronic changes.
A comparison should begin with bonding capacity and then examine oxidation-state preferences. Nitrogen favors strong multiple bonding and commonly has a maximum covalency of four, while bismuth is more strongly affected by the inert-pair effect and tends toward lower oxidation states. These contrasts provide a framework for understanding differences in structure, stability, and redox behavior.
The same deviations that alter bonding and oxidation states also influence acidity and redox chemistry. Changes in bond strength, electronegativity, and the availability of valence electrons can modify how compounds react and which forms remain stable. Recognizing these exceptions prevents broad periodic trends from being applied without considering the identity of the Group 15 element.