chapter6_mbes

=//__**Chapter 6**__//=

//**Chemical Bonding**//
== The sections studied in this chapter educate on the subject of bonding and effects on different molecules through the different types of chemical bonds, such as, covalent, ionic, and metallic. Although bonds are included in this chapter, we also learn about the importance of compounds. These important bonding and compound facts lead to the description of molecular geometry.
 * Summary**

__**——KEY POINTS**____**——**__

 * Lewis Dot Structure
 * Lewis Structures
 * Bond Overlap
 * Molecular Geometry
 * Hybridization
 * Polarity
 * Poly-Atomic Ions


 * ==In the sections below, important "need-to-know" vocabulary terms are listed as well as their definitions.==

__Introduction to Chemical bonding__

 * **Chemical Bond**-is a mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together.
 * When atoms bond, their valence electrons are redistributed in ways that make the atoms more stable.
 * **Ionic Bonding**-is a chemical bonding that result from the electrical attraction between cat-ions and an-ions.
 * **Covalent Bonding**-results from the sharing from electron pairs, between two atoms.
 * In a purely covalent bond, the shared electrons are "owned" eaually by the two bonded atoms.
 * Bonding between atoms with an electronegetivity difference of 1.7 or less has an ionic character of 50% or less.
 * **Non-Polar Covalent Bond**-covalent bond in which the bonding electrons are shared equally by the bonded atoms resulting in a balanced distribution of an electrical charge.
 * **Polar**-meaning that they have an unequal distribution.
 * **Polar Covalent Bond**-is a covalent bond which the bonded atoms have an unequal attraction for shared electron.

__Covalent Bonding and Molecular Compounds__

 * Many chemical compounds, including most of the chemicals that are in living things and are produced by living things, are composed of molecules.
 * **Molecule**-is a neutral group of atoms that are held together by covalent bonds.
 * **Molecular Compound**-a chemical compound whose simplest units are molecules.
 * **Chemical Formula**-indicates the relative numbers of atoms of each kind in a chemical compound by using atomic numbers in numerical subscripts.
 * **Molecular Formula**-shows the types and numbers of atoms combined in a single molecule of a molecular compound.
 * After the approaching nuclei become attracted to each other, they correspond to a decrease in the total potential energy of the atoms.
 * However, the two nuclei repel each other and the two electrons repel each other, resulting in an increase in potential energy.
 * **Diatomic Molecule**-a molecule containing only two atoms.
 * **Bond Energy**-is energy required to break a chemical bond and form neutral isolated atoms.
 * The Octet Rule is described when chemical compounds tend to form so that each atom, by gaining or losing, or sharing electrons has an octet of electrons in its highest occupied energy level.
 * Most main-group elements tend to form covalent bonds according to the octet rule.
 * **Electron-Dot Notation**-is an electron notation configuration in which only the valence electrons of an atom of a particular element are shown indicted by dots placed around the elements symbol.
 * **Lewis Structures**-formulas in which atomic symbols represent nuclei in inner shell election dots pairs or dashes between two atomic symbols represent electron pairs in a covalent bond and dots adjacent to only one atomic symbol represent unshared electrons.
 * The Lewis Structures for many molecules can be drawn if one knows the composition of the molecule and which atoms are bonded to each other.
 * **Structural Formula**-indicates the kind number arrangement and bonds but not the unshared pairs of the atoms in a molecule.
 * **Single Bonds**-is a covalent bond in which one pair of electrons is shared two atoms.
 * **Triple Bond**-is a covalent bond in which three pairs of electrons are shared between two atom.
 * **Multiple Bonds**-multiple covalent bonds; name of double and triple bonds.
 * **Resonance**-refers to bonding in molecules or ions that cannot be correctly represented by a single Lewis Structure.
 * To indicate resonance, a double-headed arrow is placed between a molecule's resonance structures.

__Ionic Bonding and Ionic compounds__

 * **Ionic Compound**-is composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal.
 * **Formula Unit**-is the simplest collection of atoms from which an ionic compounds formula can be established.
 * **Lattice Energy**-is the energy released when one mole of an ionic crystalline compound is formed form gaseous ions.
 * Lattice energy values for a few common ionic compounds.
 * The force that holds ions together in ionic compounds is a very strong overall attraction between positive and negetive charges.
 * **Polyatomic Ion**-a charged group of covalently bonded atoms.

__Metallic Bonding__

 * **Metallic Bonding**-the chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons.
 * **Malleability**-is the ability of a substance to be hammered or beaten into thin sheets.
 * **Ductility**-is the ability of a substance to be drawn, pulled, or extruded through a small opening produce a wire.




 * **VSEPR theory**-states that a repulsion between the sets of valence electrons surrounding an atom causes the sets to be oriented to be as far apart as possible (Valence, Shell, Electron, Pair, Repulsion).
 * **Hybridization**-is the mixing of two or more atomic orbital’s of similar energies on the same atom to produced new atomic hybrid orbital’s of equal energy.
 * **Hybrid Orbital’s**-are orbital’s of equal energy produced by the combination of two or more orbital’s on the same atom.
 * **Dipole**-is created by equal but opposite charges that are separated by an equal distance.
 * **Hydrogen Bonding**-the inner molecular force in which a hydrogen atom is bonded to a highly electro-negative atom is attracted to unshared pair of electrons of an electro-negative atom in a nearby molecule.
 * **London Dispersion Forces**-the inner molecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles.


 * ==IMPORTANT-==


 * =//**V**//= || =//**Valence**//= ||
 * =//**S**//= || =//**Shell**//= ||
 * =//**E**//= || =//**Electron**//= ||
 * =//**P**//= || =//**Pair**//= ||
 * =//**R**//= || =//**Repulsion**//= ||

The chart below will be very helpful in remembering the Total Pairs, Number of Bonds and Lone Pairs,and the Shape:

 * **Total Pairs**
 * Around Central Atoms** || **Bonding** || **Lone**
 * Pairs** || **Shape** ||
 * //1 or 2// || //1 or 2// || 0 || //Linear// ||
 * //3// || //3// || 0 || //Trigonal Planar// ||
 * //3// || //2// || //1// || //Bent// ||
 * //4// || //4// || 0 || //Tetrahedral// ||
 * //4// || //3// || //1// || //Trigonal Pyramidal// ||
 * //4// || //2// || //2// || //Bent// ||
 * //5// || //5// || 0 || //Trigonal Bipyramidal// ||
 * //5// || //4// || //1// || //See-Saw// ||
 * //5// || //3// || //2// || //T-Shaped// ||
 * //6// || //6// || 0 || //Octahedral// ||
 * //6// || //5// || //1// || //Square Pyramidal// ||
 * //6// || //4// || //2// || //Square Planar// ||

//**__Conclusion__**//
This chapter is very important in finding the bond types of many different chemicals. There are different chemical bond types such as covalent, ionic, and metallic but they are all laid out differently. One layout is molecular geometry which is the most important of all. All key points at the beginning of this page are also very important to this chapter and to do it correctly takes some practice. For extra practice we have provided practice problems, as well as, questions to answer about the above information and information from the chapter.

**__//Practice Problems//__** (use a separate sheet of paper)

 * Give examples of each of the following: Covalent Bond, Ionic Bond, and Metallic Bond.


 * Molecular Geometry of: BrF5; PF5; SCl6


 * Polyatomic Ions: NH4+; C2H3O2-


 * Lewis Structure: CH4; NH3


 * Lewis Dot Diagram: Li; B; N; O; Cl


 * Hybridization:CH4; NH3; CH2O


 * Bond Overlap: H2O

//__Questions__// (use a separate sheet of paper)

 * 1) What is a chemical bond?
 * 2) What determines whether atoms will form chemical bonds?
 * 3) What is the main distinction between ionic and covalent bonding?
 * 4) How many pairs of electrons are shared in the following types of covalent bonds?
 * a single bond
 * a double bond
 * a triple bond

5. Explain why most metels are malleable nd ductile but not ionic crystals are not. 6. What two theories can be used to predict molecular geometry? 7. When drawing Lewis Structures, which atom is usually the central atom? 8. What is an ionic compound?



Citations:

 * http://www.up.ac.za/academic/chem/mol_geom/mol_geometry.htm


 * http://content.answers.com/main/content/wp/en-commons/a/a9/VSEPR_geometries.PNG


 * http://www.petrakisassociates.com/background%20images/Molecules/Molecules_and_Integration.jpg


 * http://www.accessexcellence.org/RC/VL/GG/ecb/ecb_images/02_06_stable_arrangement.jpg


 * The Holt, Rinehart, and Winston, ed. Modern Chemistry. Austin: Harcourt Company, 2006.