OCHEM Week 5 (Unit 2)

Covalent compound:

formed when two nonmetals share

electrons to form a chemical bond.

Naming Binary Covalent compounds

prefix/name of 1st element + prefix base/base name of 2nd element + ide

1

mono-

2

-di

3

-tri

4

-tetra

5

-penta

6

-hexa

7

-hepta

8

-octa

9

-nona

10

-deca

Chemical/Molecular Formula:

representation of the molecule of a covalent compound, consists of the symbols of the elements followed by subscripts describing the number of each atom following the elemental symbols

Lewis structure

diagram that shows the bonding between atoms of a molecule,

and nonbonding pairs of electrons that exist in molecules.

Lone pairs

Nonbonding pairs of electrons that serve to depict the completion of atom's octet.

Lewis dot structure

diagram shows the bonding between atoms of a molecule and nonbonding pairs of e- that exist in that molecule.

VSEPR (valence-shell electron-pair repulsion theory)

theory is based on the idea that e-pairs around a central atom repel each other and arrange themselves as far apart as possible → determining the molecular shape

e- domain/group

any lone pair of e- / shared e- resulting in a single, double, or triple bond

P, Cl, S

live in period 3, can hold more than 8 e-

FC (formal charge)

# of valance e- - # of bonds - # of lone pairs

Be (2A) only wants

4 e-

B only wants

6 e-

He only wants…

2 e-

:

lone pair (nonbonding)

—

shared pair (shared e-)

E- group/domain

the way we illustrate e- in chemistry

E- domains

when VSPER theory is applied to the valence shell e- of the central atoms, the shape of the molecule can be predicted

E- domain rules

1) all valance shell e- pairs around the central atom are counted equally (bonding or lone pair)

2) single, double, or triple bonds are all considered to be a single e- domain

E- domain geometry

general shape that a molecule assumes when repulsions are minimized between e- domains, calcualted via bonding domains

Molecular geometry shape

3D shape of bonded atoms in a molecule, calculated via nonbonding domains (lone pairs)

2 bonding domains

linear in e- domain/molecular geometry, 180 bond angle

Bent

trigonal planar (1 lone pair) or tetrahedral (2 lone pairs)

3 e- domains

= trigonal planar

4 e- domains

= tetrahedral

Tetrahedral + 1 lone pair =

trigonal pyramidal

tetrahedral + 2 lone pairs =

bent

Polarity

the distribution of electrical charge between bonded atoms

Electronegativity

tendency for an atom to attract e-

Nonpolar covalent bond

covalent bonding when the e- is shared equally by the bonded atoms

Bond polarization

a result of shared e- being attracted to the more electronegative atom of a bond pair of atoms (e- shift in bond)

Polar covalent bond

a covalent bond that shows bond polarization; thus the bondding e- gets shared unequally (= unequal sharing)

More electroneg. an atom is =

partial neg charge (-)

the less electroneg an atom is =

partial pos charge (+)

<0.4 EN =

nonpolar bond

0.4 - 1.8 EN =

polar covalent

>1.8 EN =

ionic bond

Polar molecule

a molecule that contains polarized bonds —> result in charges that are distributed non-symmetrically throughout molecule

nonpolar molecule

a molecule that contains no polarized bonds/molecule that contains polarized bonds —> result in symmetrical distribution of charges throughout molecule

How to determine overall polarity of a molecule

use e- deomain geometry

Linear

= nonpolar

trigonal planar

nonpolar

tetrahedral

= nonpolar