Chemical Bonding

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Chemical Bonding

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A force that holds groups of two or more atoms together and makes them function as a unit

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Bond Energy

Back 2

The energy that is required to break down a bond

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Ionic Bonding: Electronegativity

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The tendency of an atom in a molecule to attract shared electrons to itself

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Cations

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Remove 1 electron-----> +1 cation
Remove 2----->+2 Cation and so on
Removing electrons creates a POSITIVE IONS are called Cations
Metals always form CATIONS (+) Alkali Metals ---> +1, Alkalike Earth Metals ----> +2, Boron Group ---->+3

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Ion

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An charged atom called an ion can be created by adding OR removing one or more Electrons. NOTE: IONS are NEVER formed by changing the number of protons!

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Anion

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Adding electrons creates a negative ion called Anion.
ADD 1 Electron---->-1 anion
Non-metals always form ANIONS (-) Oxygen Group ---> -2 and halogens -1

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Ionic Compounds

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Conduct electricity in liquid phase
Net charge is zero
total (+) charge + toatal (-) charge=zero net charge
Use criss-cross method; look pge 18 week 8

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Ionic Compound Structure

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Slide 20 picture
The actual solid contains huge and equal numbers of LI+ and F- ions packed together in a way that maximized the attractions of oppoistely charged ions;
CATIONS are always SMALLER than the parent atom (loose electrons)
Anions are always Larger than the parent atom (gain electrons)

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Covalent Bonding

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See chart for relative electronegativity differance, relative strength, types of atoms, pure vs.polar covalent

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Valence Electrons

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Electrons in the outermost (highest) principal energy level of an atom
Elements in the same group on the PT have diff # of total electrons but the same number of valence electrons

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Valence Electrons In atoms

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how are they shared between atoms? Need to draw lewis structure. A reprensention of a molecue that shows how the VALENCE ELECTRONS are arranged among the atoms in the molecule. lewis structures only show valence electrons dont forget that each atoms still contain all of its no-valence electrons noted in its comple electron congfiguration

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Lewis Structures

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Show valences electrons ; two shared electrons forms a bond b-ween atoms; electrons are arranged so atom is surrounded by alot of atoms to fill the valence orbitals of that atom

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Octet Rule

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Atoms have full or shared possession of eight electrons to be stable like noble gases or 8 electrons needed

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Duet Rule

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Hydrogen's valence orbitals are full with 2 electrons

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Single Bond

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All of the example we have seen so far have only one bond between atoms example
H-H

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Double Bond

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H::H Carbon Dioxide (CO2) Total valence electrons=4+6+6=16

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Lewis Structure

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Is a reprensintation of a moleule that shows how the valence electrons are arranged among the atoms in the molecule

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Single bond

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involves two atoms sharing one electron pair

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Double bond

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involves two atoms sharing two pairs of electrons

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VSEPR Model

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Valence shell electron pair repulsion model is usful for prediction the molecular structures of molecules formed from nonmetals
# Of pairs 2 Name of arrangment linear
Number of pairs 3 name of arrangement Trigonal planar
Number of pairs 4 Name of arrangement Tetrahedral

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Binary Compounds Type 1

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Metal only can form ONE type of cation; rules r cation is always named 1st and the anion 2nd; simple cation obtained from a single atom takes its name from the name of the element; simple anion obtained from a single atom is named by taking the first part of elemtn name the root and adding "ide"

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Binary Compounds Examples type 1

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Binary compounds contain two elements Bi--> means 2 so metal and no-Metal ionic compound (types 1 and 2)

EX: NaCl Sodium Chloride, NaL sodium iodide, CaO calcium oxide, MgBr magnesium bromide

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Binary Compounds Examples type 2

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Two non - metals covalent compound type 3 Meyal only can form more than one type of cation transition metals
iron-->Fe3 or Fe 2+ or Copper --> Cue 2+ or Cu+ Roman numerals I=one, II=two, III= Three, IV=four, Cation is always named first and the anion second, b the cation can assume more than one charge, the charge is specified by roman numeral in parentheses . CuCl Copper (I)Chloride, HgO Mercury (II)Oxide, Fe2 O3 iron (III) oxide, MnO2 Maganese (IV)oxide

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Binary Compounds Examples Type 3

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1st element in formula named first & full element name is used, 2nd element is named as though it were an anion, preifxes are used to denote the # of atoms present, prefix "mono" is never used for naming the 1st element

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Binary Compounds Examples Type 3

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CO- carbon monoxide, BF3 boron trifluride, NO- nitrogen monoxide, N2O5 dinitrogen pentoxide

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Polyatomic Ions

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Poly--->means many not all ions contain only one element, contain secerl atoms of diff emt bonded covalently, each diffrent ion has a special name, compounds containg these ions are named very similar to binary compounds
Examples Na2SO4 sodium sulfate, Fe(No3)3 iron (III)nitrate, KH2PO4 potassium dihdrogen phosphate

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Writting Formulas from names

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See example on power point chapter 8 slide 53

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Chemical Equations

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They represent a written form of chemical reaction (chemical change) showing the starting material (reactants) and ending amterial (products) of the reaction

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What is occuring during a reaction?

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When a reaction occurs the arrangement of the atoms in the starting reactant changes creating new product compound though breaking of some bonds and the forming of other bonds.

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In a chemical reaction atoms are never created nor destoryed

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the toms are only rearranged

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Reactants Vs. Products

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Reactants (starting materials) Products (ending materials)

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Balancing equation
Why is balancing equations nessecary?

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the same number and type of atoms have to exist in both the reactants and the products of the chemical reaction( mass coversion)

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Coefficient Vs. Subscripts

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Coefficients show the ration of the reactants and the products for the reaction, always simplifed to the smallest whole num ratio

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Stoichiometry Atomic Mass (atoms)

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Fror an single atom of an element/on periodic table. Amu>unified atomic mass unit
1 amu=1.66x10neg24 g Example cptr 10 pg 8 -12 amu realated to grams

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Amu/Atom

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How much does 100 carbon atoms weigh in amu? SEE pg 8

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g/mol

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See pg 13

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Mole

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Mole (mol)= 6.022x10^23 units in avogadro's number; an element with a mass equal to that element's av atomic mass expreessed in g contains 1 mol of atoms

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Molar Mass to calculate moles and number of molecules

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See examples pg 21 week 10

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Forumlas

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see back page of week 10

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Mole Ratios

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See slide 4 week 11