Prelim 1 Flashcards
How many bonds does C need for an octet?
4 bonds
What is a stable octet?
8 valence electrons
What do Lewis structures consist of?
Lewis structures consist of:
- dots showing individual electrons
- “lone pairs”, which are 2 electrons next to each other
- 1-3 lines between 2 atoms (can be the same type of atom) indicating a bond
- the shorthand for the atom name (ex: C, N, H, O, etc.) written at the ends of each line indicating the atoms bonded to each other
What do condensed structures look like?
Condensed structures are a shorthand for drawing Lewis structures that consist of the atoms of the Lewis structures written in an ordered, single line.
Ex: CH3CH2CH2CH2CH2CH3 or CH3(CH2)4CH3
*Pretend the 3 is a subscript
What are the rules for creating condensed structures?
- Atoms of the longest chain* must be written
horizontally - Ligands (atoms that are bound to another atom) are
written to the atom’s right
Ex: NH3 (H3, the ligand, is written to the right of N) - Lone pairs of e- are not shown
- Collapsing atoms
- Subscripts are used to depict the # of atoms - Parentheses used to depict polyatomic ligands bonded
to another atom
Ex: HOCH2CH2CH(NH2)CH3 - Bonds to C are omitted
- If necessary, use explicit bonds to clarify
attachment
*What counts as the “longest chain” depends on the molecule
What do Lewis structures look like?
Lewis structures:
H H H H H | | | | | H --- C ---- C --- C ---- C ---- C --- H | | | | | H H H H H
What do line-bond/skeletal structures look like?
/\/\/
What are the rules for creating line-bond/skeletal structures?
- Every “corner” is a C (unless labeled otherwise)
- Every line end is a C (unless labeled otherwise)
- Hs on Cs are invisible
- Exception: If C is explicitly written, then its bonded
Hs must be written - Hs on heteroatoms drawn, not necessarily w/ a bond
- It CAN be drawn w/ a bond if you want to draw it - Lone pairs (non-bonding e-) on heteroatoms are
optional
- Exception: If the lone pair(s) are being used in a
mechanism/indicated you must draw them - Complete octets on nearly everything
- Exception: H (2 ve-), sometimes B*, etc.
What’s special about Halogens?
- Halogens have 8 ve-
- Halogens do not make bonds because they are stable
How to find the number of ve- in an atom?
Consult the periodic table:
- At the top of each column in some periodic tables it will have a number 1-8, which informs you how many valence electrons the elements in that column has
How many lone pairs are assumed in O?
2 lone pairs (4 electrons)
How many lone pairs are assumed in N?
1 lone pair (2 electrons)
How many lone pairs are assumed in Br?
3 lone pairs ( 6 electrons)
What is the rule for nonbonding e- on C?
Non-bonding e- on C must be explicitly drawn.
What is the rule for nonzero formal charges?
Nonzero formal changes MUST be shown.
What is the formal charge of a C w/ one bond?
The formal charge does not exist.
What is the formal charge of a C w/ 3 bonds?
- Positive
- Negative
- No formal charge
What is the formal charge of an N w/ 1 bond?
- The formal charge does not exist.
What is the formal charge of an N w/ 2 bonds?
- Positive
What is the formal charge of an N w/ 3 bonds?
- No formal charge
What is the formal charge of an N w/ 4 bonds?
- Positive
What is the formal charge of an O w/ 1 bond?
- Negative
What is the formal charge of an O w/ 2 bonds?
- No formal charge
What is the formal charge of an O w/ 3 bonds?
- Positive
What is the formal charge of an O w/ 4 bonds?
- The formal charge does not exist
What is the formal charge of a halogen w/ 1 bond?
- No formal charge
What is the formal charge of a halogen w/ 2 bonds?
- Positive
What is the formal charge of a halogen w/ 3 bonds?
- The formal charge does not exist
What is the formal charge of a halogen w/ 4 bonds?
- The formal charge does not exist
How many ve- does C have?
4 ve-
How many ve- does H have?
1 ve-
How many ve- does O have?
6 ve-
How many ve- does N have?
5 ve-
How many ve- does P have?
5 ve-
How many ve- does S have?
6 ve-
How many bonds does H need for an octet?
1 bond
How many bonds does O need for an octet?
2 bonds
How many bonds does N need for an octet?
3 bonds
How many bonds does P need for an octet?
3 bonds
How many bonds does S need for an octet?
2 bonds
How to determine the number of ve- (in an entire molecule)
- Find the sum of all the different ve- contributions from every atom present in the molecule
Ex: Find the number of ve- in H2S
*Pretend 2 is a subscript
H: 1 ve- S: 6 ve- # ve- = 1 ve- + 1ve- + 6ve- = 8ve-
(2 Hs= 2 ve-)
Hydrocarbon w/ CC single bonds.
- Alkane
Hydrocarbon w/ CC double bonds
- Alkene
Hydrocarbon w/ CC triple bonds
- Alkyne
A functional group where in the hydrocarbon setup, a halogen(s) will take the place of hydrogen. (single bond)
-Halide
-ane
- Alkane
-ene
- Alkene
-yne
- Alkyne
C single bonded to one OH group
- Alcohol
-ol
- Alcohol
C single bonded to one SH group
- Thiol
-thiol
- Thiol
O single bonded to C on either side
- Ether
-sulfide
- Sulfide
S single bonded to C on either side
- Sulfide
-disulfide
- Disulfide
2 Ss single-bonded to each other and single-bonded to one C on either side
- Disulfide
-amine
- Amine
C single bonded to N
- Amine
C double bonded to N
- Imine