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Chemical Bonds Project
Transcript of Chemical Bonds Project
Examples in the household would be table salt, baking soda, cleaning ammonia, Epsom salt, vinegar, and bleach. http://upload.wikimedia.org/wikipedia/commons/a/a8/NaF.gif In the above animation, Sodium and fluorine bond ionically to form sodium fluoride. Sodium loses its outer electron to give it a stable electron configuration, and this electron enters the fluorine atom exothermically. The oppositely charged ions are then attracted to each other. When sodium is burned in a chlorine atmosphere, it produces the compound sodium chloride. This has a high melting point (800 ºC) and dissolves in water to give a conducting solution. Sodium chloride is an ionic compound, and the crystalline solid has the structure shown in the next interactive model. Transfer of the lone electron of a sodium atom to the half-filled orbital of a chlorine atom generates a sodium cation and a chloride anion. Electrostatic attraction results in these oppositely charged ions packing together in a lattice. The attractive forces holding the ions in place can be referred to as ionic bonds. http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/models2.htm#nacl
Note: Right click to become interactive. In these examples, you can clearly see that the lone "bonding" electron of the sodium atom is transferred to the nearly full valence shell of the chlorine atom to form the ionic compound of sodium chloride. Chemical Properties Melting Point
The temperature at which a given solid will melt. The melting and boiling point of a substance is largely determine by the intermolecular forces which hold its molecules together. These may included Van der Waals forces (dispersion forces), dipole-dipole interactions, as well as hydrogen bonding. The stronger these forces act between molecules, the high the melting point and boiling point of the substance.
Example: Water melts at 0 degrees Celsius. Boiling Point
The temperature at which a liquid boils and turns to vapor.
The stronger the intermolecular forces are (per molecule), the higher the boiling point will be, as it will require a greater amount of heat energy to overcome the intermolecular forces that hold molecules in a liquid state.
Example: The boiling point for fresh water at sea level is 212°F (100°C). Solubility
The quantity of a particular substance that can dissolve in a particular solvent (yielding a saturated solution) due to the London and Dipole-Dipole forces acting upon the substance.
Example: According to the solubility chart, Sodium Hydroxide is only slightly soluble. Malleable
Able to be hammered or pressed permanently out of shape without breaking or cracking. This is due to the "sea of electrons." Because they can all spread out amongst themselves, they have more potential to be hammered or pressed without breaking.
Example: Bronze can be beaten, hammered or pressed without cracking or breaking. Ductile
(of a metal) Able to be drawn out into a thin wire. Or-- Able to be deformed without losing toughness; pliable, not brittle. This is also due to the "sea of electrons." Because they can all spread out amongst themselves, they have more potential to be hammered or pressed without breaking.
Example: Copper is very ductile-- most household wiring is copper. Using the "octet rule" this ionic compound satisfies Chlorine's nearly full valence level with the outermost electron of Sodiums' furthest energy level. In this example, the "Lewis Diagram" model shows you the outermost valence electron being transferred to Chlorine, thus creating an ionic bond. (Covalent Bonds) A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. Examples of covalently bonded molecules you could find in you home are; soap, detergent, sugar, artificial sweeteners, vanilla, syrup, alcohol and starch. Stereo chemical Formulas And Structural Diagrams Examples of covalent bonding shown above include hydrogen, fluorine, carbon dioxide and carbon tetrafluoride. These illustrations use a simple Bohr notation, with valence electrons designated by colored dots. Note that in the first case both hydrogen atoms achieve a helium-like pair of 1s-electrons by sharing. In the other examples carbon, oxygen and fluorine achieve neon-like valence octets by a similar sharing of electron pairs. Carbon dioxide is notable because it is a case in which two pairs of electrons (four in all) are shared by the same two atoms. This is an example of a double covalent bond. Covalent chemical bonds involve the sharing of a pair of valence electrons by two atoms, in contrast to the transfer of electrons in ionic bonds. Such bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom.Hydrogen gas forms the simplest covalent bond in the diatomic hydrogen molecule. The halogens such as chlorine also exist as diatomic gases by forming covalent bonds. The nitrogen and oxygen which makes up the bulk of the atmosphere also exhibits covalent bonding in forming diatomic molecules. A different attractive interaction between atoms, called covalent bonding, is involved here. Covalent bonding occurs by a sharing of valence electrons, rather than an outright electron transfer. Similarities in physical properties (they are all gases) suggest that the diatomic elements H2, N2, O2, F2 & Cl2 also have covalent bonds. A Crystal Lattice is a three-dimensional configuration of points connected by lines used to describe the orderly arrangement of atoms in a crystal. Each point represents one or more atoms in the actual crystal. The lattice is divided into a number of identical blocks or cells that are repeated in all directions to form a geometric pattern. Lattices are classified according to their dominant symmetries: isometric, trigonal, hexagonal, tetragonal, orthorhombic, monoclinic, and triclinic. Compounds that exhibit a crystal-lattice structure include sodium chloride (table salt), cesium chloride, and boron nitride. Metallic bonding constitutes the electrostatic attractive forces between the delocalized electrons, called conduction electrons, gathered in an electron cloud, and the positively charged metal ions. Understood as the sharing of "free" electrons among a lattice of positively charged ions (cations)
In a more quantum-mechanical view, the conduction electrons divide their density equally over all atoms that function as neutral (non-charged) entities. Metallic bonding accounts for many physical properties of metals, such as strength, malleability, ductility, thermal and electrical conductivity, opacity, and luster. Essentially, all metallic bonding is, is a whole bunch of positively charged nuclei, swimming in a sea of negatively charged electrons (sharing.) Whilst swimming, they develop strong ties to each other. Therefore metals often have high melting or boiling points. The principle is similar to that of ionic bonds.Because the electrons move independently of the positive ions in a sea of negative charge, the metal gains some electrical conductivity. It allows the energy to pass quickly through the electrons generating a current. Heat conduction works on the same principle - the free electrons can transfer the energy at a faster rate than other substances such as those which are covalently bonded, as these have their electrons fixed into position. There also are few non-metals which conduct electricity: graphite (because, like metals, they have free electrons), and molten and aqueous ionic compounds which have free moving ions. Fun Fact!
Metal bonds have at least one valence electron which they do not share with neighboring atoms, and they do not lose electrons to form ions. Instead the outer energy levels (atomic orbitals) of the metal atoms overlap. Therefore, metallic bonds are actually very similar to covalent bonds. Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. An important branch of stereochemistry is the study of chiral molecules. Stereochemistry is also known as 3D chemistry because the prefix "stereo-" means "three-dimensionality".The study of Stereochemistry focuses on stereoisomers and spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecular chemistry. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question (dynamic stereochemistry). Just an example of how to turn a Lewis Diagram into a Structural Formula. A Tetrahedral shaped molecule. A Pyramidal shaped molecule. A Trigonal Planar Molecule. An Angular shaped molecule. A Linear shaped molecule.