Chapter 4 Lecture

Question 1

molecular formulas

Answer 1

shows atoms within molecule + proportions of the atom

Question 2

structural formulas

Answer 2

line-bond structures that give more information vs. the molecular formula (connections of the atoms)

Question 3

how do you draw structural formulas?

Answer 3

1. know how many covalent bonds an atom can form
2. count total # of valence electrons
3. use covalent bonds to connect atoms to each other
4. add onto central atoms - add pairs of electrons to complete octets
5. add other lone pairs

Question 4

condensed strucutral formulas

Answer 4

abbreviated formulas

Question 5

skeletal structures

Answer 5

no letters shown; covalent bonds are presented by lines

Question 6

covalent bonds

Answer 6

atoms that share a pair of valence electrons

Question 7

electronegativity

Answer 7

defined as the ability of atom to attract bonding electrons - sometimes electrons are not always shared equally

Question 8

nonpolar covalent bonds

Answer 8

the difference in electronegativity is less than 0.5 - not significant enough (equal sharing of bonding electrons)

Question 9

polar covalent bonds

Answer 9

the difference in electronegativity is between 0.5-0.9 - significant enough (unequal sharing of bonding electrons)

Question 10

ionic bonds

Answer 10

the difference in electronegativity is more than 0.9 (creation of an ionic bond)

Question 11

drawing polar covalent bonds

Answer 11

• head of arrow always points to more electronegative atom
• determines polarity of molecule
• polar molecules dissolve in water

Question 12

polarity

Answer 12

one end of the molecule is positive, and another end is negative

Question 13

rules for polarity

Answer 13

• if a molecule contains only one non-polar bond, it is always NONPOLAR
• for a molecule to be polar, it must have AT LEAST ONE POLAR BOND
• not ALL molecules containing polar covalent bonds are polar

Question 14

what are some of the molecular 3d shapes?

Answer 14

• tetrahedral
• bent
• linear
• pyramidal
  *have to know # of bonds and lone pairs of electrons
  *electrons are as far apart as possible

Question 15

what are the non-covalent interactions?

Answer 15

these are attractive interactions that do not involve the sharing of valence electrons
-relatively weak, but become strong once in large quantities

Question 16

permanent partial charges

Answer 16

• hydrogen bonds
• dipole-dipole interactions

Question 17

temporary partial charges

Answer 17

• london forces - hydrophobic forces

Question 18

dipole-dipole bond

Answer 18

attraction of neighboring polar groups to one another

Question 19

hydrogen bonds

Answer 19

interaction of an electronegative atoms (like N or O) with an H atom that is covalently attached to another electronegative atom (N or O)

Question 20

london forces

Answer 20

nonpolar molecules (or basic nonpolar portions of a molecule) that are “attracted” to one another
- just means our hydrophobic molecules are avoiding water as much as possible - just looks like “attraction”
- greater contact of non-polar areas, the stronger the force !

Question 21

organic chemistry

Answer 21

the study of C-based compounds

Question 22

functional groups

Answer 22

an atom or groups of atoms or bonds that give the molecule a particular set of chemical properties