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CHEMICAL BONDING  the TRANSFER Or SHARING of Electrons

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CHEMICAL BONDING  the TRANSFER Or SHARING of Electrons CHEMICAL BONDING The TRANSFER or SHARING of electrons. In the formation of chemical compounds from elements, valence electrons are usually either: a. transferred from the outer shell of one atom to the outer shell of another atom and b. shared among the outer shells of the combining atoms. Ways to PRODUCE A CHEMICAL BOND: 1) IONIC BONDING~ transfer of electrons from one atom to another. The compound formed is called IONIC COMPOUND & the type of bond formed is an IONIC BOND. Usually metals + non-metals produce ionic bonds. The compds they produce are vast crystal lattices. Ex. 11 Na + 17 Cl NaCl Electronic Configuration: Na 1s2 2s2 2p6 3s1 Cl 1s2 2s2 2p6 3s2 3p5 .. Electron Dot Formula: Na Cl : .. Na atom losses 1 e, while Cl atom accepts to follow the octet rule. Na atom becomes Na ion (cation) Cl atom becomes Cl ion (anion) IONS~ are charged particles created when atoms either LOSE or GAIN ELECTRONS. CATIONS ~ are positively charged ions. Usually METALS. ANIONS ~ are negatively charged ions. Usually NON-METALS. IONIZATION ENERGY ~ the energy needed to remove an electron in an atom. 2) COVALENT BONDING~ sharing of electrons between two atoms, usually non-metals. The type of bond formed is the COVALENT BOND & they produce Covalent Compounds. Usually non-metals + non-metals produce covalent bonds. Ex. 1H + 1H H2 Electronic Configuration: H: 1s1 H: 1s1 Electron Dot Formula: H + H H : H MOLECULE~ a chemical structure held together by Covalent Bonds. SELF TEST: 1) Show the formation of a chemical bond of the following: a. Magnesium Bromide (MgBr2) d. N2 b. O2 e. NaCl c. Al2S3 f. H2 SO4 3) MULTIPLE BONDING~ a bond of electrons attained in several types of bonding such as: a) Single Covalent Bond – attained in a single pair. Ex: H + H H : H or H – H or H2 b) Double Covalent Bond – when 2 pairs of electrons are sharing between 2 nuclei represented by 2 dashes ( = ) Ex. CO2 c) Triple Covalent Bond – when 3 pairs of electrons are sharing & represented by 3 dashes ( = ) . Ex. Nitrogen (N2) ~ is found in the atmosphere as a diatomic molecule. Each N atom has 5 valence electrons & need to share 3 electrons. The 3 shared pair electrons will form a triple bond by 3 dashes. Accounts for 80% of the of the gases in the atmosphere, stable; relatively UNREACTIVE. Because of being unreactive, Nitrogen is in the form of N2, useless to most forms of life. There is only 1 type of organism that utilize the atmospheric nitrogen—BACTERIA. They live on soil or in roots of plants such as peas & alfalfa. Roots—contains NODULES these nodules contain the Nitrogen-Fixing Bacteria. Using the nutrient provided through the roots, these bacteria CONVERT the Nitrogen in the air to form AMMONIA (NH3) or NITRATES (NO3). These compds w/c resulted upon conversion of the Nitrogen inside the roots to become compds that can be used by plants & animals then get N2 by eating the plant. Nitrogen has 5 valence e- CHEMICAL FORMULA A combination of elemental symbols and subscript numbers that is used to show the composition of a compound depending on the type of compound that the formula represents, the information that it provides will vary slightly whether it is a molecular compound or an ionic compound. TYPES OF CHEMICAL FORMULA: 1. Molecular Formula – A chemical formula that denotes the constituent elements of a molecular substance & the # of atoms of each element composing 1 molecule. Ex. C6 H6 (benzene) H2O2 (hydrogen peroxide) 2. Empirical Formula – A special type of chemical formula, that shows the composition of a molecule not as it actually exists, but in a simple whole number ratio. Ex. CH HO Ionic compounds are composed of charged ions that are held together by electrostatic forces. A typical type of ionic compound, called a binary compound because it is made up of two elements, will be composed of metallic positive ions (cations) and nonmetal negative ions (anions). Another type of ionic compound, called a ternary compound as it contains three elements, is composed of monatomic ions and polyatomic ions. When dealing with ionic formulas it is very important to remember that the formula does not show how the compound actually exists in nature. It only shows the ratio by which the individual ions combine. Ex. The ionic formula for calcium chloride is CaCl2. Since calcium chloride is an ionic compound, this formula does not mean that there are actually two chlorine atoms floating around attached to one calcium atom. Ionic compounds are actually continuous, lacking the discrete units that make up a sample of a molecular substance. Rather, the formula shows that a sample of calcium chloride contains twice as many chlorine atoms as calcium atoms. Remember that ionic compounds are not molecules, so the formula CaCl2 is said to represent one formula unit of calcium chloride. Molecular compounds are held together by covalent bonds, or shared pairs of electrons. Molecular formulas do show these molecules as they actually exist as discrete units in nature. Ex. When we say that the molecular formula of water is H2O, we can see that the molecules of water are made up of three atoms; two hydrogen atoms are covalently bonded to each oxygen atom. Isomerism - is the phenomenon whereby certain compounds, with the same molecular formula, exist in different forms owing to their different organisations of atoms. The concept of isomerism illustrates the fundamental importance of molecular structure and shape in organic chemistry. Isomers are molecules that have the same chemical formula but different structural formulas. CH3CH2 CH2 CH2 CH2CH3 or C6H14 or hexane CH3 I CH3 CH2 CH CH2 CH3 or Hexane Structural Isomerism Structural Isomers have different structural formulae because their atoms are linked together in different ways. It arises owing to: • arrangement of Carbon skeleton e.g. The formula C4H10 represents two possible structural formulae, butane and methylpropane: • position of Functional group e.g. propan-1-ol and propan-2-ol • different Functional groups e.g. the molecular formula C2H60 represents both ethanol and methoxymethane. ethanol Dimethyl ether ethyl alcohol, pure alcohol, grain alcohol IUPAC: methoxymethane or drinking alcohol Cyclic alkanes are isomeric with alkenes, e.g. cyclopropane and propene FUNCTIONAL GROUP Organic Chemistry Essentials Many important organic chemistry molecules contain oxygen or nitrogen. It's a good idea to memorize the names and structures of these functional groups. Benzyl acetate Has an ester functional group (in red), an acetyl moiety (circled with green) and a benzyl alcohol moiety (circled with orange). Other divisions can be made. In organic chemistry, functional groups -- are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of. However, its relative reactivity can be modified by nearby functional groups. The word moiety is often used synonymously to "functional group," but, according to the IUPAC definition, a moiety -- is a part of a molecule that may include functional groups as substructures. For example: ester A carboxylic acid ester. R and R' denote any alkyl( or aryl (functional)group Esters are usually derived from an inorganic acid or organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group, and most commonly from carboxylic acids and alcohols. Is divided into an alcohol moiety and an acyl moiety, but has an ester functional group. Also, it may be divided into carboxylate and alkyl moieties. Combining the names of functional groups with the names of the parent alkanes generates a powerful systematic nomenclature for naming organic compounds. The atoms of functional groups are linked to each other and to the rest of the molecule by covalent bonds. When the group of atoms is associated with the rest of the molecule primarily by ionic forces, the group is referred to more properly as a polyatomic ion or complex ion. ( POLYATOMIC IONS~ a group of covalently bonded atoms, that as a group, carries an electrical charge, but since it is so stable, it can through most chem. rxns as a unit won’t come apart.) And all of these are called radicals, by a meaning of the term radical that predates the free radical. The first carbon atom after the carbon that attaches to the functional group is called the alpha carbon; the second, beta carbon, the third, gamma carbon, etc. If there is another functional group at a carbon, it may be named with the Greek letter, e.g. the gamma- amine in gamma-aminobutanoic acid is on the third carbon of the carbon chain attached to the carboxylic acid group. II The HYDROCARBONS In Organic Chemistry it is the simplest organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called -- hydrocarbyls. (organic chemistry) Any univalent radical, derived from a hydrocarbon, such as methyl or phenyl. Aromatic hydrocarbons (arenes), alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons. The majority of hydrocarbons found naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate -- to form atoms of the same chemical element into a chain held together by chemical bonds. A) Alkanes Organic Chemistry Nomenclature & Numbering A saturated hydrocarbon in which all of the carbon-carbon bonds are single bonds. Each carbon atom forms four bonds and each hydrogen forms a single bond to a carbon. The bonding around each carbon atom is tetrahedral, so all bond angles are 109.5°.
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