Chemistry Chapter 12 Study Guide

VSEPR-Valence Shell Electron Pair Repulsion Stars(*) means most common

# of Regions # of bonds Geometry 4 *tetrahedral 4(lines to4&1) 3 pyramidal 2 *Bent(109.5)V-shaped 1 Linear _______________________________________________ 3*Trigonal planar(triangular) 3(lines to 3&1) 2 Bent(120 degrees) 1 Linear _______________________________________________ 2 *Linear 2(lines to both) 1 *Linear example: Sodium Chloride

Example: N2 (Just to be clear the 2 is supposed to be a subscript)

:N=N:

Bond Angle

angle formed across 2 adjacent bonds in a molecule.

Ionic Compound

compound that results when a metal reacts with a nonmetal to form cations and anions.

Polar Covalent Bonding

covalent bond in which the electrons are not shared equally because one atom attracts them more strongly than the other.

Lewis Structure

diagram of a molecule showing how the valence electrons are arranged among the atoms in the molecule.

Lone Pairs or Unshared Pairs

electron parts that are localized on a given atom and not involved in bonding.

Covalent Bonding

electrons are shared by the nuclei, atoms share electrons.

Tetrahedral Arrangement

figure formed by connecting lines with the arrangement of electron pairs.

Trigonal Pyramid

molecular structure of ammonia, one side is different from the other 3.

Tetrahedral Structure or Tetrahedron

molecular structure, 4 identical triangular faces.

Covalent(Nonmetals)

share electrons. *All elements want octet* Look at CO2 that's the example Mrs. Detty did for this.

Why are the valence electrons of an atom the only electrons likely to be involved in bonding to other atoms?

The electrons have the highest energy level, and are transferred when a metal and a nonmetal react to form an ionic compound.

Write the Lewis structure for Xe.

Xe (z=54) Xe is in group 8 therefore it gets 8 dots. Kr in the picture would be an example.

Bond

a force that holds groups of 2 or more atoms together and makes them function as a unit.

Bonding Pair

electron pair found in the space between 2 atoms.

Trigonal Planar Structure

structure with triangular structures

Molecular Structure or Geometric Structure

the 3-D arrangement of atoms in a molecule.

Resonance Structure

various Lewis Structures

Duet Rule

when a molecule form has the atoms combined to have 2 electrons in their valence shells. H2 is an example of this.

Dipole Moment

when a molecule has a center of a positive and negative charge.

Octet Rule

when atoms of non-metals form the most stable molecules that are surrounded by 8 electrons in the valence orbit.

Resonance

when more than one Lewis Structures can be drawn for the molecule. The electron structure is an average of all of them.

Write the simple Lewis structure for I.

I (z=53) Iodine is in group 7 therefore it gets 7 dots. An example would be like CL in the picture.

Periodic Table with Groups Labeled Good Luck Everyone!

If this picture doesn't work well..use your own, google, or find a friend:)

Linear Structure

all atoms in a line.

Write the Lewis structure for AL.

AL (z=13) AL is in group 3 therefore it gets 3 dots.

Using the VSEPR theory, predict the molecular structure of PH3

Trigonal Planar . . H-P-H | H

Resonance

*More than 1 Lewis Structure is possible* NO3-1 Covalent, It pulls from oxygen(whichever one it wants).I think it has a lone pair.

Ionic (Metal and Nonmetal)

*only one element(always nonmetal) has a full octet* As you can see CL has 7 dots including 1 from the line(-). *(-) that means 2 dots which is a pair of electrons.* 1 pair= 2 .. Na-CL : ..

Steps for Writing Lewis Structure

1. Obtain the sum of the valence electrons from all of the atoms. It is the total number of valence electrons. 2. Use one pair of electrons to form a bond between each pair of bound atoms. 3.Arrange the remaining electrons to satisfy the duet rule(when hydrogen shares 2 electrons) for hydrogen and the octet rule(8 electrons) for each 2nd row element. O2 ** ** O = O ** **

What is the geometric structure of the water molecule? How many pairs of valence electrons are there on the oxygen atom in the water molecule? What is the approximate H-O-H bond angle in water?

105 degrees, Bent or V-shaped, 2 pairs O / \ H H

Double Bond

2 atoms sharing 2 pairs of electrons

Single Bond

2 atoms sharing one electron pair

How many electrons are involved when 2 atoms in a molecule are connected by a "double bond"? Write the Lewis structure of a molecule containing a double bond.

2 pairs of electrons.

Triple Bond

3 electron pairs are shared

Example: OH-1

Basically what the picture is except there needs to be brackets separating O and H from a -1. Like in the CL picture(question before this)

Using the VSEPR theory, predict the molecular structure of OCL2

Bent or V-shaped . . . . : CL -O- CL : . . . .

Example #5 H2O

Bent(109.5 degrees) . . H-O-H . .

Using the VSEPR theory, predict the molecular structure of H2SE

Bent(109.5 degrees), Linear

Example: C2 (2=subscript)

C=C *there are supposed to be 2 of these(=) which means there should be 4 lines between the 2 C's*

Write the Lewis structure for for the simple molecules. Show all bonding valence electron pairs as lines and all non bonding valence electron pairs as dots. CBr4

Find a pic or replace H with Br on G(pic)

Why are all diatomic molecules linear, regardless of the number of valence electron pairs on the atoms involved?

Geometry shows that only two points in space are needed to indicate a straight line. A diatomic molecule represents two points in space.

Example: NH4+1

H '=a dot H.** .*H * ' * H [ H ] +1 | [ H-N-H ] | [ H ] Don't forget your brackets!!!Look in book/your own notes for a better picture.

Polar Covalent(Hydrogen Bonding)

H is happy with 2 electrons, all other elements have octet. O's=* and H=^ ** H^ *O* ^H **

Ions Cl-1

Here she did 7 x's and 1 dot=8 electrons with brackets around this and a -1 since chlorine has a negative charge.** Always put brackets when an element has a negative charge** [****]-1 It would look like this but [*CL^] prettier&better on paper. [**] Also, 1 bracket on each side which equals 2 brackets total.

Example#1 BeCL2

Linear . . . . : CL-Be-CL : . . . .

Draw possible resonance structures for sulforphane.

Look at this pic or the one from 12.6-12.7 Pg.298(#63)

Write the Lewis structure for the simple molecules. Show all bonding valence electron pairs as lines and all non bonding valence electron pairs as dots. NBr3

Look up pic . . . . . . : Br-N-. Br: . . . . | : Br : . .

Examples#1 N

N is in group number 15 *(But u only need 5 dots)*

Using the VSEPR theory, predict the molecular structure of NCL3

NCL3=Pyramidal, Trigonal Planar

Example#2 O

O is in group 16 *(But u only need 6 dots)*

Example #2 BF3

Polar Covalent, Trigonal Planar(triangular)

Example #4 NH3

Pyramidal

Write the Lewis structure for Sr.

Sr (z=38) Sr is in group 2 therefore it gets 2 dots. . . Sr

Using the VSEPR theory, predict the molecular structure of CBr4

Tetrahedral, G would be an example in the pic except Br instead of H. . . : Br : . . | . . : Br - C - Br : . . | . . : Br : . .

Using the VSEPR theory, predict the molecular structure of SiCL4

Tetrahedral, No lone pairs

Example #3 CH4

Tetrahedral, no lone pairs

What general principles determine the molecular structure (shape) of a molecule?

The general molecular structure of a molecule is determined by how many electron pairs surround the central atom in the molecule, and by which of those pairs are used for bonding to the other atoms of the molecule.

What is the geometric culture of the ammonia molecule? How many pairs of electrons surround the nitrogen atom in NH3? What is the approximate H-N-H bond angle in ammonia?

Trigonal Pyramid, 3 pairs, less than 109.5%

Lewis Structures=graphic representation of valence electrons.

Valence-outside and electrons associated with bonding. Bonding Pairs(-)those electrons actually involved in the bond. Lone Pairs(.. or ** etc.)-electrons not involved with a bond. Examples: Li* or Mg^^(Doesn't matter how you represent them).

Ionic Bonding

the attraction between oppositely charged ions.

Bond Energy

the energy required to break a given chemical bond.

Valence-Shell Electron-Pair Repulsion Theory (VSEPR)

the main postulate of which is that the structure around a given atom in a molecule that minimizes electron-pair repulsions.

Electronegativity

the relative ability of an atom in a molecule to attract shared electrons to itself.