Chemical Bonding Flashcards
What is Electron Negativity?
The ability to attract a shared pair of electrons
What is a covalent bond?
2 attoms share a pair of electrons equally
What is a polar covalent bond?
when one side of a covalently bonded atom has a greater electron negativity pulling the electrons closer to it making it slightly negative
can you get a polar bond but not a polar atom?
yes, polar bonds can cancel each other out.
what is the Pouling scale?
it is a scale that assigns each element a value of electron negativity
what factors effect EN (electron negativity)
nuclear charge
atomic structure
shielding
what difference in EN (electron negativity) makes a pure covalent bond?
less than 1.0
what difference in EN (electron negativity) makes a polar covalent bond?
between 1.0 and 2.0
what difference in EN (electron negativity) makes a ionic bond?
more than 2.0
what is a polar molocule
when one atom in a covalently bonded molecule has a larger EN the electrons are pulled slightly towards it creating different polls on either side of the molecule
true or falce. Polar bonds always make polar molocules
Falce. some polar bonds cancel each other
what do you call a shell that has more than 8 electrons
electron ritch or expanding the octet
what do you call a shell that has less than 8 electrons?
electron-deficient
what is a ionic bond formed by?
a meatal and a non-meatal
what is a co-ordinate bond or a dative covalant bond?
it is a covalent bond where the shared pair of electrons come from the same atom (must have a lone pair to happen)
what is metallic bonding?
it is when meatals are held together by electrostatic forces
true or false. at high temperatures aluminium chloride can be a monomer
True
what is a dimer?
two molecules bonded together
what is hybridisation?
when two shells combine to form a complete orbital
what is the dipole moment?
a measure of how polar a molecule is
explain an S - S bond
when two S orbitals bond it is called a sigma bond, they bond head on and they combine orbitals with one electron to form a full orbital
explain a P - P bond
when two P orbital bond together side on we call this a pi bond they overlap at two points to share electrons thus making them stronger than sigma bonds
true or false. pi bonds are stronger than sigma bonds
True
define bond energy
the energy required to break one mole of a particular covalent in the gaseous state (measured in kilojoule per mol)
define bond length
the internuclear distance between the nucleus of two atoms (shorter bond is strongest e.g triple bond is the shortest and strongest)
what is a picometer
1x10^-12 of a meter and used to measure bond length
what factors affect the reactivity of covalent bonds?
polarity of bond
strength of bond
type of bond (sigma or pi)
what are diatomic molocules?
F2
Cl2
I2
what group are the halogens?
group 17
which group has the highest electron negativity?
the halogens (they make the most polar bonds)
what is VSEPR theory
valence shell electron pair repulsion (can predict the molecular shape and bond angles of molecules)
give the order of repulsion in VSEPR theory
(lone pair - lone pair) > (lone pair-bond pair) > (bond pair - bond pair)
what is the agle of a linear molecule?
180 degrees
what is the angle between bonds of a trigonal plainer?
120 degrees
what is the angle between bonds of a Trigonal Pyramidal?
107 degrees
what is the angle between bonds of a Tetrahedral?
109.5 degrees
what is the angle between bonds of a trigonal bipyramidal
120 and 90 degrees
what is the angle between bonds on a octahedral?
90 degrees
intramolecular bond
a bond within a molecule (i.e between two atoms)
intermolecular force (IMF)
forces (sometimes bonds) between molecules.
what bonds have the highest IMF (intramolecular force)
hydrogen bonds (pd - pd bond)
define a dipole
a molecule that has a slight charge difference across it
define a species
atom or molocule
what is needed for hydrogen bond?
- a species with an O or N with an available lone Pair
- a species with an -OH or -NH group
what does the number of hydrogen bonds in one atom depend on?
the number of lone pairs (i.e no molecule can have more than two hydrogen bonds)
what properties does hydrogen give whater?
High melting and boiling points
High surface tension
anomalous densitys of ice compared to water
what is the enthalpy of vaporisation?
the energy required to boil a substance
define a hidride
anything that contains a hydrogen
define an instantanius dipole
a type of IMF that is temporary (id - id forces)
in what molecules do instantaneous dipoles occur?
all molecules but especially in non-polar molecules (chances increase with the number of electrons)
define surface tention
the ability of a liquid surface to resist any external forces (I.e the stay unaffected by forces action on the surface)
why is surface tention a thing
because intermolecular forces between the surface and lower molecules pull the surface molecules down towards the water and to each other above it
what is a dipole moment?
a measure of how polar a molecule is
how do you show which is the negative end of polar molecule?
point an arrow towards the negative end of the molocule
what are van der waals forces?
they are intermolecular forces between molecules
what are id - id (instantanius dipole) forces also know as?
London dispersion forces
what are London dispersion forces caused by?
a shift in the electron cloud in a molecule
when will london dispersion forces increce?
increces with elecron and atomic number but also in places where molocules come close together
what are the strongest to weakest bonds
Covalent bond
ionic bond
Metalic bond
hydrogen bond
pd - pd forces
id - id forces
