Chem Bonding, Molec Geometry and Polarity, Phys Char, and IMFS

Chemical Bond

How atoms chemically interact with each other to achieve stability

Ion

The charged particle from an Ionic Bond

Molecule

The result from a covalent bond

Ionic Bond

A bond formed by the complete transfer of valence electrons between metals and non-metals

Covalent Bond

The bond formed by the sharing of valence electrons between two non-metals 

Intramolecular Forces

Forces that hold atoms together within a molecule (Chemical Bonds)

Intermolecular Forces

Forces of attraction between molecules (Dipole-Dipole, Ion-Dipole, Hydrogen Bonds, LDFS)

Why does Ice Float?

The crystalline structure of the molecules due to hydrogen bonding when freezing 

How do detergents work?

Detergents harness IMFs to clean by interacting with both water and oily substances

Why do substances dissolve in water while others don’t?

Substances with similar IMFS to water tend to dissolve well. This principle is summarized as “like dissolves like”

How do adhesives work?

Establishing contact with surfaces and harnessing various IMFS, including dispersion, dipole-dipole, and hydrogen bonds to create strong bonds

Do IMFS govern all physical changes?

Yes, like phase changes, medium changes, solubility, and molecular transport within biotic and abiotic systems

What do temperature changes affect?

Affects Particle Kinetic Energy

What does Pressure changes affect?

Affects particle collisions and spacing (molecules get closer together)

What does Medium Changes Effect?

Different environments affect solubility

Sublimation 

Solid to Gas

Deposition

Gas to Solid Directly

Dissolution

Substance dissolves in solvent

Diffusion

Particles move from high to low concentration

Molecular transport

Movement across barriers (like cell membranes)

Do stronger IMFSs need more energy for phase changes

Yes

London Dispersion Forces (LDFS)

• Special type of Van der Waal Force

• Weakest type of IMF

• Caused by temporary electron shifts creating temporary dipoles

• Strength increases with the number of electrons (larger molecules)

  • In all type of molecules

Dipole-Dipole Forces

• Occur between any polar molecules

• Permanent uneven distribution of electrons

• Partially positive end attracts the negative end

  • Stronger than LDFs because they’re permanent

Hydrogen Bonds 

• Special case of dipole-dipole forces

• Occurs when H is bonded to N, O, or F

• Much stronger than Dipole-Dipole Forces

  • Water has unusually high boiling points due to H-bonds

Ion-Dipole Forces

• Strongest type of IMF

• It occurs between ions and polar molecules

• Important in dissolution and compounds

  • Example: When NaCI dissolves in water

Electronegativity

The power of an atom in a molecule to attract electrons to itself

Physical Changes

Rearrange existing Particles

The weakest type of intermolecular force is

London Dispersion Forces

What’s stronger Intermolecular forces (Hydrogen Bonds, Dipole-Dipole) or Intramolecular bonds

Intramolecular bond

List the IMF from weakest to strongest

London-Dispersion Forces, Dipole-Dipole Forces, Hydrogen Bonds, Ion-Dipole Forces

Molecular Geometry

The 3D arrangement of atoms in a molecule, which determines the shape of a molecule T

Tetrahedral 

Central atom connected to 4 other atoms through single bonds 

• Example: Methane (CH4)

Pyramidal

The central atom is connected to 3 other atoms through single bonds

• Has 1 lone pair of electrons

  • Example: Ammonia (NH3)

Bent Geometry 

Central atom connected to two other atoms through single bonds

• Has two lone pairs of electrons

• Example: Water (H2O)

Linear Geometry

Atoms arranged in a straight line

• Can have single, double, or triple bonds (180 degrees)

  • Example: Carbon Dioxide (CO2)

Diatomic Molecules (Have No Fear Of Ice Cold Baths)

All diatomic molecules are automatically linear in geometry

Molecular Polarity

Refers to the distribution of electrons within a molecule and is influenced by both molecular geometry and electronegativity

Polar Molecules

Uneven sharing of electrons between atoms

• Asymmetrical electron distribution

  • Examples: Water (Bent), and Ammonia (Pyramidal)

Nonpolar Molecules

Even sharing of electrons between atoms

• Symmetrical electron distribution

  • Examples: CH4 (Tetrahedral) CO2 (Linear)

Are all pyramidal and bent molecules polar?

Yes due to the lone pairs

Are all linear and tetrahedral molecules nonpolar?

They can be polar or nonpolar (must evaluate symmetry)

Do Polar Solutes dissolve in Polar Solvents

Yes

Do Nonpolar solutes dissolve in Nonpolar solutes dissolve in Nonpolar solvents 

Yes