Chemistry Chapter 8 and 9  

Lattice Energy - enegry to conber solid ionic to gas ions

  • the formation of these bonds realease energy

when looking at a lattice cube it represents a solid

Melting can relatively quantify lattice energy because it takes more energy to break

Lattice energy is one of the strongest bonding forces

Electronegativity and Polarity

  • two types of strong bonds
      * Covalent '
      * ionic
  • fro the bonds inbetween there are polar bonds
  • A nonpolar covalent bonds have no diffenec in electron negitivity
  • Bonds with a diffeence in electo negtiviy ar Polar bonds
      * For example Br-Br is nonpolar
      * C-Br is Polar because one wants the elctrons mor than the other and they have 2 different poles (dipoles)
  • Ionic bonds (NaF) usually between Metals and nonmetals
  • Electronegativity varies in position on the periodic table
  • Electron affinity is the atom by itself and electron negativity is the atom in a compound
  • halogens have highest electronegative because they are one away from a stable octect
  • a bond between atoms are non polar covalent when the difference is les that .5
  • .5 -2 is polar covalent
  • greater than 2 is ionic
  • A metal and a nonmetal is ionic

The s is a partial charge (negative or positive)

From left to rights elctronegeitiviiy increases

From bottom to top electronegtiviy increases

Polar covalent bonds

Dipole Moments - whats going on with bond polarity

  • the more electronegative get the parial negative
  • Cross arrow also show the patial negative
  • For patiall negative and partal positive allways pick the one that fartheest from florine to be positive
  • Dipoles always depends whay it is paird on
  • \

Lewis dot symbols

Group 1A and Group 7A- tend to form one bond

all elctron assoiated witht the highest priciple qunatum number are valence

One dot goes in each box for each valence electron

Show ions with that lose wot a plus

Show ions that gain with the full shells and a minus

Drawing Lewis structures

Step1 - Cont the total numver of valence electrons Present, ad for negative charges subtract for positive charges

Step 2- Draw the skeletal structur of the compound, the lease electronegative atom is usually the central atom and eac fo the surrounding atoms

Step 3- use the remaining elecrons to complete octets of the terminal atoms by placing pairs of electrons on each atom , complete the octeet of the most electronegative atom first

Step 4 - place any reaming atoms on the central elctron

Step 5 - IF the central atom ahas fewer than eight electrons move one or more pairs from the terminal atoms to forme multipe bonds bewteen the central atom and terminal atoms.

Reasonance structures are structures with differnt ways to write them, arrows are draw to show they are reasonate

Formal charge - used to determin the most plausible lewis structure when more thatn one possiblity exist from a compund

Formal charge = valecne e- -- assoicated e-

all the adtoms non bonding electrons are assoiated with the atom

half the atoms bodnign electron s bonding atoms are assoinatied with

Free Radicals - Molecules with an odd number or electrons

 

Octets are obeyed for 2P elements

Molecular Geometry

VSEPR valence chell electon pair pefulsion

linear bonds are 180 degrees

Trigonall Panar = 120 degree

Techrahedral 109.5 degrees

Trigonal bypyrimainal

Intermolecular forces

Gives insight on physical or chemicals properties

  • Dispersion forces
      * anything with electrons has dispersion forces (protons do not )
      * an atom with more elcrons has higer dispersion forces
      * The shape (contact area) of a molecule disrupts dispersion forces
      * the more contact area the greater dispersion force
      * The greater the dispersion the more difficult it is to boil/ melt
  • Dipole - dipole
      * requires a permeant dipole
      * they interact with other dipoles
      * Dipoles connect more negative side to more positive side
      * Dipole - Dipole interactions have greater intermolecular forces that molecules with only dispersion forces
  • Hydrogen bonds
      * Stronger that dipole dipole bonds
      * covalent bonds between H O N or F
  • dipole incuced dipoles
      * Temporary dipole from a nonpolar and a polar bond
  • Ion dipole
  • ion ion
      * This is the strongest
  • ion/ induced

Valence bond theroy

  • all single bonds are sigma bonds but all sigma bonds aren’t single bonds
  • Hybridixzed bonds make bonds even
  • when a bond is hybridized the obitals are combined
  • a single bonds is one domain a double bond is
  • Parallel P orbitals make pi bonds

Steps to hybridized bonds

  1. Count the electron domains, this is your amount of orbitals