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How do atoms make compounds? Typically they join together in such a way that they lose their identities as elements and adopt a new identity as a compound. These joins are called chemical bonds. But how do atoms join together? Ultimately, it all comes down to electrons. Before we discuss how electrons interact, we need to introduce a tool to simply illustrate electrons in an atom. In this lesson you will learn :
1. Lewis Dot Symbols
1. Lewis Dot Symbols
A Lewis dot symbol consists of the symbol of an element and one dot for each valence electron in an atom of the element. These dots are arranged to the right and left and above and below the symbol, with no more than two dots on a side. (It does not matter what order the positions are used). Take a look the following figure about the Lewis dot symbol of elements. Elements in the same group have similar outer electron configurations and hence similar Lewis dot symbols. Lewis electron dot diagrams for ions have less (for cations) or more (for anions) dots than the corresponding atom.
2. The Ionic Bond
2. The Ionic Bond
An ionic bond is the electrostatic force that holds ions together in an ionic compound. As a rule, the elements most likely to form cations in ionic compounds are the alkali metals and alkaline earth metals, and the elements most likely to form anions are the halogens and oxygen. Lets say the reaction between Lithium and Fluorine, the electrostatic attraction happens between the positive charged of Lithium and negative charged of Fluorine, the compound itself is neutral. The reaction starts with the ionization of Lithium atom to give Li+that reacts with F- from the ionization reaction of Fluorine atom.
3. Lattice Energy of Ionic Compounds
3. Lattice Energy of Ionic Compounds
A quantitative measure of the stability of any ionic solid is its lattice energy, defined as the energy required to completely separate one mole of a solid ionic compound into gaseous ions. Lattice energy is determined by the charge of the ions and the distance between the ions. Lattice energy can not be measured directly, we can calculate the compound's lattice energy using Coulomb's law. Indirectly procedure that we called as Born-Haber cycle relates lattice energies of ionic compounds to ionization energies, electron affinities, and other atomic and molecular properties.
The greater the lattice energy, the more stable the ionic compound. Keep in mind that lattice energy is always a positive quantity because the separation of ions in a solid into ions in the gas phase is, by Coulomb’s law, an endothermic process. The larger the lattice energy, the more stable the solid and the more tightly held the ions. It takes more energy to melt such a solid, and so the solid has a higher melting point than one with a smaller lattice energy.
4. The Covalent Bond
4. The Covalent Bond
5. Electronegativity
5. Electronegativity
6. Writing Lewis Structures
6. Writing Lewis Structures
7. Formal Charge and Lewis Structure
7. Formal Charge and Lewis Structure
8. The Concept of Resonance
8. The Concept of Resonance
9. Exceptions to the Octet Rule
9. Exceptions to the Octet Rule
10. Bond Enthalpy
10. Bond Enthalpy
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