wow i hate chem- unit 4

What are the four steps to drawing a Lewis structure?

1. draw skeletal structure of compound showing what atoms are bonded to each other. least electronegative element goes to center

2. count valence e-. add up valence. add 1 for each negative charge. subtract 1 for each positive charge

3. complete octet for all atoms except for hydrogen

4. if structure has too many e-, form double or triple bonds on central atoms as needed

What is formal charge?

the difference between the number of valence electrons in an isolated atom and the number of electrons assigned to that atom in a lewis structure

What is the formula to find formal charge?

#valence electrons - #non bonding electrons - 1/2(#bonded electrons)

What does the sum of formal charge equal?

the sum of the formal charges of the atoms in a molecule or ion must equal the charge on the molecule or ion

What are the three rules with formal charge?

1. if all atoms have a 0 formal charge, then it is good

2. it is less plausible for lewis structures to have large formal charges than small charges

3. with similar distributions of formal charges, the most plausible structure is the one in which negative formal charges are placed on the most electronegative atoms

When is the only time you an atom can have an expanded octet?

the only time an atom can have an expanded octet is if its principle quantum number is greater than 2

3rd period or below

What are the elements that form incomplete octets?

beryllium, boron, and aluminum form covalent bons

BeBAl

Beryllium has 2 bonds

Boron and aluminum have 3 bonds

What is the VSEPR theory?

Valence Shell Electron Pair Repulsion

electron pairs, whether they are bonding or lone, will try to get as far away from each other as possible

How many total attachments are there if the electron arrangement is linear?

2

If there are two attachments what is the electron arrangement?

linear

What is the electron arrangement if the molecular geometry is linear with 2 attachments?

linear

How many lone pairs are there if the electron arrangement linear when the electron arrangement is linear?

0

What is the molecular geometry if there are 2 atoms attached and 0 lone pairs?

linear

What is the angle from atom to atom when the electron arrangement in linear?

180 degrees

If there are three attachments what is the electron arrangement?

trigonal planar

What is the molecular geometry if there are 3 atoms attached and 0 lone pairs?

trigonal planar

How many total attachments are there if the electron arrangement is trigonal planar?

3

How many lone pairs are there if the molecular geometry is trigonal planar?

0

How many atoms are attached if the molecular geometry is trigonal planar?

3

What is the molecular geometry if there are 2 atoms attached and 1 lone pair?

bent

How many lone pairs are there if the molecular geometry is bent when the electron arrangement is trigonal planar?

1

How many atoms attached are there if the molecular geometry is bent?

2

What is the angle if the molecular geometry is trigonal planar?

120 degrees

What is the angle if the molecular geometry is bent and the electron arrangement is trigonal planar?

How do lone pairs affect the angles from an atom to another atom?

the lone pairs are large and take up space, which repels the other atoms pushing them closer together

If there are four attachments what is the electron arrangement?

tetrahedron

What is the molecular geometry if there are 4 atoms attached and 0 lone pairs?

tetrahedron

How many total attachments are there if the electron arrangement is tetrahedron?

4

How many lone pairs are there if the molecular geometry is tetrahedron?

0

What are the angles from atom to atom when the molecular geometry is a tetrahedron?

109.5 degrees

How many atoms are attached if the molecular geometry is tetrahedron?

4

What is the molecular geometry if there are 3 atoms attached and 1 lone pair?

trigonal pyramidal

How many atoms are attached if the molecular geometry is trigonal pyramidal?

3

How many lone pairs are attached if the molecular geometry is trigonal pyramidal?

1

What is the molecular geometry if there are 2 atoms attached and 2 lone pairs?

bent

How many atoms are attached if the molecular geometry is bent when the electron arrangement is tetrahedron?

2

How many lone pairs are attached if the molecular geometry is bent when the electron arrangement is tetrahedron?

2

What is the angle from atom to atom if the molecular geometry is trigonal pyramidal?

What is the angle from atom to atom if the molecular geometry is bent when the electron arrangement is a tetrahedron?

How many total attachments are there if the electron arrangement is trigonal bipyramidal?

5

What is the electron arrangement if there are 5 total attachments?

trigonal bipyramidal

How many atoms are attached if the molecular geometry is trigonal bipyramidal?

5

How many lone pairs are there if the molecular geometry is trigonal bipyramidal?

0

What are the angles from atom to atom when the molecular geometry is trigonal bipyramidal?

90 degrees from axial to equatorial

120 degrees from equatorial to equatorial

How many atoms are attached if the molecular geometry is a seesaw/distorted tetrahedron?

4

How many lone pairs are there if the molecular geometry is a seesaw/distorted tetrahedron?

1

What is the molecular geometry if there are 4 atoms attached and 1 lone pair?

seesaw/distorted tetrahedron

What are the angles from atom to atom in a distorted tetrahedron?

90 degrees from axial to equatorial

120 degrees from equatorial to equatorial

What is the molecular geometry if there are 3 atoms attached and 2 lone pairs?

t-shaped

How many atoms are attached if the molecular geometry is t-shaped?

3

How many lone pairs are there if the molecular geometry is t-shaped?

2

What are the angles from atom to atom in t-shaped?

90 degrees from axial to equatorial

120 degrees from equatorial to equatorial

Which atom do lone pairs replace in trigonal bipyramidal?

equatorial atoms

What is the molecular geometry if there are 2 atoms attached an 3 lone pairs?

linear

How many atoms are attached if the molecular geometry is linear and the electron arrangement is trigonal bipyramidal?

2

How many lone pairs are attached if the molecular geometry is linear and the electron arrangement is trigonal bipyramidal?

3

What is the electron arrangement when there are 6 attachments?

octahedral

What is the molecular geometry with 6 atoms attached and 0 lone pairs?

octahedral

How many atoms are attached if the molecular geometry is an octahedral?

6

How many lone pairs are attached if the molecular geometry is an octahedral?

0

What is the angle when the molecular geometry is an octahedral?

90 degrees

What is the molecular geometry with 5 atoms attached and 1 lone pair?

square pyramidal

How many lone pairs are attached if the molecular geometry is square pyramidal?

1

How many atoms are attached if the molecular geometry is square pyramidal?

5

What is the angle when the molecular geometry is square pyramidal?

90 degrees

What is the molecular geometry with 4 atoms attached and 2 lone pairs?

square planar

How many lone pairs are attached if the molecular geometry is square planar?

2

How many atoms are attached if the molecular geometry is square planar?

4

What is the angle when the molecular geometry is square planar?

90 degrees

What is a resonance structure

one of two or more lewis structures for a single molecule that cannot be represented accurately by only one lewis structure

What symbol is particular to resonance structures?

How do you draw resonance strucutres?

change where bonds and lone pairs are

When is a structure equal combination?

electrons are all shared the same in all three structures

If there are no lone pairs, how is the molecular geometry named?

named the same as the electron arrangement