interactions etc Flashcards
What is an element?
A substance which cannot be split by chemical means
What is an atom?
The smallest unit of an element, which when split open loses its characteristic chemical properties
What is the difference between relative abundance and relative atomic mass
Relative abundance refers to the percentage of a specific isotope in a sample
Relative atomic mass is the weighted mass of the entire sample
Orbitals with the same energy in a subshell are _
degenerate
equivalent orbitals in a shell are
subshells
hund’s rule
electrons will first occupy an empty orbital
reactivity of an atom depends on
the tendency of the valence electrons to interact with other atoms
a full valence shell requires
filled s and p orbitals
how many electrons confer maximum stability to an atom?
8
two non metals form
covalent bonds
non metal and metals form
ionic bonds
metals are generally found on the _ hand side of the periodictable
left
non metals are generally found on the _ hand side of the periodic table
right
ionic compounds exist in what structure
lattices, repetitive and organised patterns
which compounds don’t form discrete molecules
ionic compounds
what kinds of orbitals are formed from the overlap of two orbitals?
a low energy bonding orbital
a high energy anti-bonding orbital
what is a hypervalent atom?
one holding more than 8 electrons in a shell
give two examples of hypervalent atoms relevant to biological systems
sulfur and phosphorous
what is a dative covalent bond?
a shared pair of electrons coming from only one of the atoms participating in the bond
give an example of a compound with dative bonding
the ammonium ion NH4+
a proton shares one of nitrogens fulll orbitals
what are dative bonding important for in biological systems
binding of metals, (binding iron in haem group)
which compounds have bonds that are in between single and double bonds
aromatic conjugated systems
what forms from overlap of adjacent p orbitals?
a conjugated system
where can a conjugated system occur?
wherever there are single bonds surrounded by double bonds
give an example of a compound with a conjugated system
beta carotene, benzene ring
a resonance compound is
a hybrid of two structures
give an example of a resonance compound1
O3
what kind of compounds feature ionic and covalent bonding
polyatomic ionic compounds
give an example of a polyatomic ionic compound
calcium carbonate
what is the only prevalent polyatomic cation?
NH4+ ammonium ion
an atom which cannot form bonds is
inert
what is electronegativity?
the strength of the force of attraction which an atom can exert on an electron
what happens to electronegativity values as you move across periods
it increases
why are non-covalent molecular interactions important for specificity
they allow molecules to form a stable shape which is complementary with other molecules so that they may function together
what causes dispersion forces?
temporary unequal distributions in electrons
dipole moment is a vector pointing to
region of highest electron density
give an example of a nonpolar molecule with polar bonds
carbon dioxide
a molecule with polar bonds can be nonpolar if
symmetric orientation results in dipole effects cancelling out eachother
what are induced dipoles
when a partial negative charge in one region induces partial positive charges in neighbouring regions
what two factors increases the dispersion forces that a molecule experiences
size of molecule (greater attraction)
conformation, molecules that can get closer experience greater forces
steric repulsion operates at distances _ than dispersion forces
shorter
hydrogen bonding is dependent on the presence of
oxygen, fluorine or nitrogen
water molecules can only interact in a stable way with
polar molecules
what determines a substances physical state
the cumulative strength of the forces of molecular interactions
what is a salt bridge
when a charged amino acid side chain interacts with an oppositely charged one through ionic forces
hydrophobic forces associate _
through dispersion forces once they have been partitioned
polar molecules have _ melting and boiling points
higher, due to more interactions
sickle cell anemia causes
different shape of haemoglobin,
binds oxygen still but causes blockages and oxygen starvation
the atomic radius is
half of the distance between two atoms of same element in a covalent bond
bond length is
the sum of the atomic radii of two covalently bonded atoms
atoms with larger valence shell numbers have
larger atomic radii
as more electrons enter a valence shell, the atomic radius
goes down
greater forces of attraction between nucleus and electrons
double and triple bonds are _ than single bonds
shorter
VSEPR excludes
pi bonds
VSEPR is concerned with
bonding and non bonding pairs
valence pairs arrange themselves geometrically in order to
minimize repulsive forces
why is carbon dioxide linear?
only two bonds considered for VSEPR
the pi bonds are not considered
nonbonding pairs exert
greater repulsive forces, pushing bond angles tighter
what hybridization will occur for 4 sigma bonds?
sp3
what type of hybridizarion will occur for 2 sigma bonds
sp
pi bonds are formed from
the overlapping of unhybridized orbitals
rotation around single bonds can occur when
hybridized orbitals are symmetric round rthe bond, no disruption, bond angles conserved, minimal steric repulsion
non bonding pairs undergo hybridization, they are treated as
sigma bonds
why is rotation not possible around pi bonds
overlapm of the orbitals would be disrupted
when is rotation around a single bond not possible
if bond is part of a delocalised system
why are some bonds ni peptide bonds prevented form rotatting
due to delocalised system
the bonds in peptide bonds that can rotate are limited by
long side chains, which cause limitations due to steric repulsions
steric hindrance
peptide bonds can only rotate through _ angles
dihedral
what conformations can a cyclic compound adopt
chair, boat
