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Trends in Lattice Energy: Ion Size and Charge

Trends in Lattice Energy: Ion Size and Charge

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:

Ions as Acids and Bases

Ions as Acids and Bases

Salts with Acidic Ions
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:

Resonance

Resonance

The Lewis structure of a nitrite anion (NO2−) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O bonds.

Ionic Bonding and Electron Transfer

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.

Energy Transfer in Chemical Reactions

Energy Transfer in Chemical Reactions

Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine a person building a brick wall. The energy it takes to lift and place one brick on top of another is the kinetic energy—the energy matter possesses because of its motion. Once the wall is in place, it stores potential energy.

Ions and Ionic Charges

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...

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Updated: Feb 10, 2026

Real-time Monitoring of Ligand-receptor Interactions with Fluorescence Resonance Energy Transfer

Real-time Monitoring of Ligand-receptor Interactions with Fluorescence Resonance Energy Transfer

Published on: August 20, 2012

Fluorescence resonance energy-transfer-based fluoride ion sensor.

Roopa Venkataraj, Arindam Sarkar, C P Girijavallabhan

|May 24, 2018

Summary

This study presents a new sensor for detecting fluoride using a dye pair. The sensor shows high specificity for fluoride detection by monitoring fluorescence changes.

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Last Updated: Feb 10, 2026

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Published on: March 23, 2017

Area of Science:

Analytical Chemistry
Photochemistry
Materials Science

Background:

Fluorescence resonance energy transfer (FRET) is a powerful tool for molecular sensing.
Developing highly specific and sensitive sensors for anions like fluoride remains a challenge.
Coumarin 540a (C540a) and Rhodamine 6g (Rh6g) are photostable dyes suitable for FRET applications.

Purpose of the Study:

To develop and characterize an energy-transfer-based sensor for fluoride detection.
To investigate the sensing mechanism and specificity of the C540a-Rh6g dye pair towards fluoride.
To establish a broad-range fluoride detection method using fluorescence monitoring.

Main Methods:

Utilized a Coumarin 540a (donor) and Rhodamine 6g (acceptor) dye pair for energy transfer studies.
Investigated the effect of varying fluoride concentrations on the fluorescence emission of both dyes in acetonitrile.
Analyzed the fluorescence resonance energy transfer efficiency in response to fluoride and other anions.

Main Results:

Fluoride concentration was found to decrease the energy transfer efficiency between C540a and Rh6g.
A recovery of fluorescence emission from C540a was observed with increasing fluoride levels.
The sensor demonstrated high specificity for fluoride compared to other tested anions.
Broad-range fluoride detection was achieved by monitoring the fluorescence of both dyes.

Conclusions:

The C540a-Rh6g dye pair enables effective energy-transfer-based fluoride sensing.
The developed sensor exhibits high specificity and a broad detection range for fluoride.
This approach offers a promising method for sensitive and selective fluoride detection.