Gen. Chem Ch.3 Bonding, Chemical Interactions

Front 1

Chemical Bond

Back 1

Attractive forces that bond elements to form molecules-Valence electrons of combined atoms

Front 2

Octet Rule

Back 2

most atoms bond according to Octet Rule.

• Atoms tend to bond with other atoms so that it has eight electrons in outermost shell-
• most stable at 8 val. e-
• Exceptions

- Hydrogen(2val)

-Li, Be bond for 2 or 4 val e-

-B: bonds for 6 val e-

all electrons period 3 or greater: can expand+8 w/ d-orbitals

ex: Cl can form seven covalent bonds- total of 14 e- in valence shell

Front 3

Octet Rule exceptions

Back 3

• Incomplete Octet: elements stable w/ <8 val e- includes: Hydrogen(2) He(2), Li(2), Be(4), B(6)
• 
  
• Expanded Octet: >period 3, can hold >8vale- includes: P(10), S(12), Cl(14) and many others
• 
  
• Odd Number e-: any molecule w/ odd val e- cannot distribute to yield 8 val e-

ex: Nitric Oxide(NO) has seven val e-

Front 4

Ionic Bonds

Back 4

electrons w/ element of low ionization energy(usually metals) transfer to element w/ high electron affinity (typically nonmetal)

-ex: NaCl

* resulting electrostatic attraction between opposite charges holds ions together like NaCl

• anion+cation

-creates lattice structures

Front 5

Covalent Bonding

Back 5

electron pair shared between two atoms-typically nonmetals (similar E.N)

• Sharing of e- forms single, double- triple bonds
• C-C Longest bond----weakest bond strength
• C=C Medium length bond--medium strength
• Triple C-C bond: shortest, strongest
• 
  

Bond Energy: energy to break a bond(more bonding=more energy to break)

Polarity: atom with highest electronegativity gets larger share of electron density

• creates dipole (partial +(least EN) and -(most EN))
• 
  

Polar Bonds can be polar, coordinate

Front 6

Cations vs Anions

Back 6

Ioninc Bonding w/ diff. electronegativities

CaTion (metal) loses electrons to become (+)

ANion(Nonmetal) gain e- to become (--) ions

Front 7

Diatomic Elements

Back 7

Most group 7, except H2

include : H2, N2, O2, F2, Cl2, Br2, and I2

Front 8

Polar Covalent Bond

Back 8

diff. in electronegatives(partial + and -)

electronegative difference between 0.5 and 1.7

• >1.7 is an ionic bond
• can measure a dipole moment(partial + and -) Dipole moment(p)= qd

-- Vector quantity (C/m), q is magnitude of charge, d is displacement

Front 9

Coordinate Covalent Bond

Back 9

Shared e- in covalent bond all from the same atom

--> normal, when lone pair of one atom attacks another atom w/ unhybrid p-orbital

ex: Lewis acid( electrophilic) accepts electrons /attacked by/from lewis basic(Nucleophilic w/ the e- to share)

Front 10

Lewis Structures

Back 10

Only show diff. possible ways atoms can be combined to form diff compounds/ or resonance

diff compound- differ in bond connectivity

resonance: only moving lone pairs

use #valence electrons to form onds

- complete octet central atom, then outside, then add lone pairs

Formal Charge: valence electrons- bond#- #lonepairs

*best lewis structures: small, or no formal charge

- less separation between opp. charges

-w/ neg. charge, best stable w/ most EN atom`

Front 11

VESPR Theory-Geometry and Polarity

Back 11

uses Lewis Dot structure to obtain 3D arrangement of atoms surrounding a central atom

determined by repulsion of bonding and nonbonding e- pairs in valence of central atom

- arrange as far apart to minimize repulsion forces

AX2 linear 180 angle between e- pairs

AX3 trigonal planar 120 angle between pairs

AX4 Tetrahedral (pyramid w/ 3 sides) 109.5 ang

AX5 trigonal bipyramidal 90, 120, and 180

AX6 Octahedral 90 180

***Electronic geometry( spatial arrangement of ALL pairs of e- around central atom)

**Molecular Geometry( spatial arrang. of just bonding pairs of e-)

Front 12

Electronic Geometry vs Molecular Geometry

Back 12

***Electronic geometry( spatial arrangement of ALL pairs of e- around central atom)**Molecular Geometry( spatial arrang. of just bonding pairs of e-)

ex: CH4 and NH3 and H2O

electronic geometry: all three have 4 e- pairs around central atom-------> tetrahedral

molecularly: differ in # e- pairs,

- CH4 tetrahedral

-NH3 trigonal Planar

-H2O is bent/angular

Front 13

Intermolecular Forces- weak electrostatic interactions

Back 13

forces between atoms and compounds

impact Melting and boiling points

--determines state of substance-solid/liquid/gas

--determines whether two substances are miscible(mix) or immiscible(form aqueous and organic layer)

Dispersion-London Forces: weakest forces

Dipole-dipole Interactions: intermediate strenght

Hydrogen Bond:: strongest(no actual transfer of H)

Front 14

London Dispersion Forces

Back 14

weak intermolecular force

random unequal distrib.of e- orbiting causing instant polar/counterpolarization---

shortlived dipole moment

in add.--> dipole causes nearby clouds to interact, polar/counterpolar

**only in close proximity are they present

**depends on degree of ease in polarizing molecule

farther electrons from nucleus(large molecules) more easily polarized

Front 15

London Dispersion forces most important for

Back 15

noble gases not liquefying at any temp.

- only intermolec. force between noble gas atoms

-require extremely low temp to liquefy noble gas( bc small mag. of dispersion forces)

Front 16

Dipole-Dipole Interactions

Back 16

energetically favorable for opposite ends to be closest to each other- electrostatic force formed between two molecules

------- dash lines----- (part. + and -)

temporary bonding

present in: solids and liquids- negligible@ gas(inc. distance)

higher melting and boiling points than nonpolar species******w/ sim. Molec weight

only diff. than L-D forces b/c is longer duration(permanence)

Front 17

Hydrogen Bonds

Back 17

strong dipole-dipole (intra or intermolecular)

---no sharing or transferring of H-----

H w/ high E.N. atom( N, O, F): H e- density very low

H w/ high EN: essentially a naked proton

-- will react w/ s(-) of F, O, N on nearby molecules

**w/ H bonding have very high boiling points

Front 18

H-Bonding Acronym

(only molecules H bonding ocurrs w/)

Back 18

Hydrogens pick up the F.O.N(phone)