molecule stuff

  • Molecular Shapes

    • Molecules when in 3D have shapes

    • Lone pair

      • Two electrons in an atom that already have each other as a pair

    • Bonding pairs

      • Electrons in an atom that can be bonded with another atom’s electron 

    • Drawing 3D molecules

      • Bonds in the plane of the paper is a normal straight line

        • The max number of atoms in the plane of the paper is 3

      • Bonds pointing towards you are wedged

      • Bonds pointing away are dashed 

    • Shape of 3D molecules 

      • This is based on what the atoms are charged

        • The most negative will be the most electronegative 

          • CO3H2

          • The hydrogens will point up instead of down since they are both slightly positive they repel and go up to avoid each other

            • They attract to the oxygens since they are slightly negative 

      • Linear

        • A straight line

          • Cl2

      • Bent

        • It bends in the middle or twice in the bond

          • H2S

      • Trigonal Pyramid

        • Has three pointing out in the same plane direction 

          • NH3

      • Tetrahedral

        • Has four in different directions

          • CH2Cl2

    • Simple Organic Nomenclature

      • Prefix

        • How many carbons

      • Suffix

        • Tells how many bonds

          • Alkane is single bond between the carbons

          • Alkene is double bonds between carbons

          • Alkyne is triple bonds between carbons

# of Carbons

Prefix

Alkane

Alkene

Alkyne

1

meth-

Methane CH4

2

eth-

Ethane C2H6

Ethene C2H4

Ethyne C2H2

3

prop-

Propane

Propene

Propyne

4

but-

Butane

Butene

Butyne

5

pent-

Pentane

6

hex-

Hexane

7

hept-

Heptane

8

oct-

Octane

9

non-

Nonane

10

dec-

Decane

  • Intermolecular Forces

    • Water 

      • With H2O the hydrogens perform a dipole moment 

        • The hydrogens point upwards towards the atom since the negative hydrogens attract the positive atom

        • The two lone pairs of electrons are at the top of the atom

          • These also have two dipole moments pointing upwards away from the hydrogens(-) towards another atom

    • Dipole Vectors with polarity

      • Combine the electronegativities 

        • The more electronegative something is the more negative it will be

        • The less electronegative it will be more positive 

      • Draw the charge vectors with a positive arrow going from the positive particle to the negative particle 

        • Account for the polarity of the bonds AND the polarity of the lone pairs 

          • Lone pair vectors always point outwards from the molecule

        • There should be a vector for each bond and each lone pair

      • If the vectors balance out and are equal on both sides then it is non-polar

        • If there is no resultant vector than it is non polar 

        • The lone pairs here are symmetric so they cancel out and everything stays balanced 

  • Characteristics of Ionic, Covalent, and Metallic substances 

    • Solubility of any substance depends on polarity

      • Polar substances will dissolve in polar solvents 

        • water(universal solvent)

      • Non polar substances will dissolve in in nonpolar solvents

        • oil

    • Ionic compounds

      • The representative unit is a formula unit 

        • A molecule is the smallest unit

      • The bonds form through the metal transferring electrons to the non metal 

      • Are usually brittle solids 

        • The physical structure is a crystal lattice because there is very strong attraction between the molecules

      • This arrangement leads to high melting and boiling points, making them distinct from molecular compounds. Additionally, these compounds typically conduct electricity when dissolved in water or melted, due to the mobility of the ions within the lattice. This conductivity is a key characteristic that differentiates ionic compounds from covalent compounds, which do not conduct electricity in the same manner.

  • Molecular compounds

    • These substances are molecular compounds held together by covalent bonds

    • The representative unit is a formula unit

      • A molecule

    • The electrons are shared between multiple atoms

    • The IMFs between the molecules are very weak 

    • Therefore they are usually gases at room temperature but can be soft solids as well

      • When the gases are solid they are brittle solids 

    • Also have low melting points

    • They are not conductors 

      • Because 

  • Metallic substances

    • The representative unit is the formula unit

      • An atom for a regular metallic compound 

    • Most metallic compounds are only one element 

      • The metals bond together and there forms kernels and the sea of electrons

        • The kernels are everything but the electrons(the nucleus of the atom)

          • The kernels form a lattice structure making it a hard solid

      • The electrons become delocalized and flow throughout the metal solid

        • The electrons are zipping all over the place while the kernels are still

      • The electrons hold the metal together due to attraction to the kernels 

    • There can also be alloys which are mixes of different metals

      • Different elements stuck to each other and attracted because of their electrons zipping around 

    • They are solids but they are malleable and ductile 

    • They are good conductors because their electrons are delocalized 

      • In this case the electrons cause the conductivity not the ions since they have much less mass

  • Miscibility

    • The ability to be mixed

    • Always liquids

    • Polar and polar are miscible and non polar and nonpolar are miscible

      • However nonpolar and polar will not mix(immiscible)

  • Bonds can be polar but molecules can be nonpolar