Chemical Bonding Flashcards
covalent bonds
break and form new bonds
formed when 2 atoms share electrons
non-covalent bonds
weak attractions between atoms with different partial charges within dipoles that don’t share electrons
van der waals forces
london dispersion forces
ionic bonds
hydrogen bonds
hydrophobic interactions
london dispersion forces
induced dipole- induced dipole
occurs when 2 molecules are close together
mutual attraction with weak temporary dipole moment
more pronounced in larger nonpolar molecules because larger electron cloud, so increased polarization
ionic bonds
salt bridge
2 charged atoms attracted to opposite charges
complete transfer of electrons from atom with low electronegativity to high electronegativity
dipole-dipole interactions
type of noncovalent bond that occurs between polar molecules with a net dipole moment
align in such a way that partial negative charge is pulled toward the partial positive charge
diatomic molecules
hydrogen, nitrogen, oxygen, fluorine, iodine, chlorine, and bromine
form covalent bonds to get full outer shell and be more stable
polar covalent bond
unequal sharing of electrons which creates an electric dipole
nonpolar covalent bond
equal sharing of electrons
bond dissociation energy
energy required to break a chemical bond
related to the bond length (distance between nuclei of bonded atoms)
shorter bonds are stronger and require more energy to break
What makes bonds stronger?
shorter bonds with small atomic radii
these will be closer to the top of the periodic table because moving toward indicated that another electron shell and therefore a larger atomic radius
What type of bonds do hydrogen make
short strong bonds
polar covalent bond
unequal sharing of electrons which creates an electric dipole
nonpolar covalent bond
equal sharing of electrons
bond dissociation energy
energy required to break a chemical bond
related to the bond length (distance between nuclei of bonded atoms)
shorter bonds are stronger and require more energy to break
What makes bonds stronger?
shorter bonds with small atomic radii
these will be closer to the top of the periodic table because moving toward indicated that another electron shell and therefore a larger atomic radius
What type of bonds do hydrogen make
short strong bonds
dipole moment
occurs when positive charge accumulates at one end of the molecule and negative charge accumulates at the other
the greater the difference in charge, the greater the dipole moment
additive effect: same direction increases dipole moment; opposite direction can cancel out
do symmetrical molecules have a net dipole moment?
typically no because dipole moments are canceled out by being in opposite directions
electron affinity
quantitative measure of the energy change when an electron is added to an atom in the gas state
the more negative the change in energy, the more energy released upon addition of electron
Why does Oxygen have the lowest electron affinity in the 6A group?
oxygen holds its electrons very close to the core which results in greater electron-electron repulsion
When an electron is shielded
shielding occurs as valence electrons move away from the positive nucleus
electrons can shield each other from the pull of the nucleus, decreases the attraction between the electron and the nucleus as electrons move away from the nucleus
Water as a solvent
water can dissolve many polar and ionic compounds because can interact well through hydrogen bonding and electrostatic interactions
- water is more electronegative than hydrogen which results in a dipole interaction - makes water more desirable to interact with
- bent geometry of water contributes to its polarity by grouping positive charges at one end of the molecule and negative charges at the other
- water’s small size allows efficient formation of a hydration shell around solutes
solvent
substance that dissolves a solute, resulting in a solution
surface tension
force induced between a liquid and a gas
molecules in the liquid interact with each other more strongly than with molecules in the air, causing the surface of the liquid to behave as a thin film
What does the freezing point depend on?
strength of intermolecular forces
freezing occurs when the kinetic energy of a molecule can no longer overcome the intermolecular forces binding it to nearby molecules
colligative properties
properties affected by the amount but no the identity of the solute
hydrogen bonding
strong intermolecular force that occurs between hydrogen atom and an electronegative atom with lone electron pair
can only occur over short distances so require small electronegative atoms –> F, O, N
sigma bonds
overlap end to end
- low energy state and very stable because lots of overlap
- very strong alone
pi bonds
overlap of p orbitals perpendicularly
- high energy state and not stable so require less energy to break (small dissociation energy)
- weak bonds when alone
- double bonds are strong because there is both a sigma and a pi bond
bond length and dissociation
the longer the bond length (sigma bonds are long, pi bonds are short), the more energy needed to break the bond
aka the longer the bond length, the more dissociation energy needed
disproportionate reaction
atoms of the same element undergo both oxidation and reduction
Ag oxidation
+1
Cd oxidation
+2
Zn oxidation
+2
Ga oxidation
+3
Al oxidation
+3
coordination chemistry - metals
metals can act as Lewis acids because they have empty valence orbitals that can readily accept electrons
Order that electrons are removed from shell?
electrons are removed from the valence electron shell with the greatest principle quantum number first because they electrons are the furthest from the nucleus and therefore the least tightly bound
ex: [Xe]6s^2 4f^7 5d^1
removed would be 6s then 5d then 4f
What would happen to the van der waals force if you replaced valine with alanine?
the london dispersion force would decrease because valine is a larger molecule and will have a greater electron cloud causing the molecule to be more polarized
replacing it with alanine (smaller molecule) will decrease the interaction
