Bonding Flashcards
co-ordinate / dative
covalent bond when both electrons are supplied by one atom
shown by arrow
often forms charged molecules
acceptor atom must bc electron deficient
lone pair donated by one atom to another
crystal structure, eg. NaCl
high. mp
conduct electricity when dissolved or molten
brittle
general good solubility
diamond
macromolecular
C bonded to 4 C
strong, hard
does not conduct electricity
conducts heat
insoluble
refracts lights; sparkles
graphite
macromolecular
C bonded to 3 C
free electrons
weak bonds between layers
low density; far apart layers
high mp
insoluble- strong covalent
how do electron pairs arrange themselves
repel each other
largest bond angle possible to minimise repulsion
lone pair
non bonding pairs
lone/bonding repulsion
L-L > L-B > B-B
linear
2 electron pairs
180
trigonal planar
3 electron pairs
120
trigonal pyramidal
tetrahedral
4 electron pairs
no lone pairs
109.5
trigonal pyramidal
4 electron pairs
1 lone pair
107
bent
4 electron pairs
2 lone pairs
104.5
trigonal bipyramidal
5 electron pairs
no lone pairs
120, 90
seesaw
5 electron pairs
1 lone pair
102, 87
T-shaped
5 electron pairs
2 lone pairs
88
octahedral
6 electron pairs
no lone pairs
90
square planar
6 electron pairs
2 lone pairs
90
electronegativity
power of an atom to attract the pair of electrons in a covalent bond
may be unsymmetrical, produces polar bond
most electronegative
Fluorine
electronegativity across a period
increases
more protons
smaller radius
same shielding
electronegativity down a group
decreases
increased radius
increased shielding
permanent dipole-dipole
different electronegativies
polar bond
stronger than vdw
temporary dipole / van der waals
electron orbitals are influenced by another charged particle
in all molecules
electrons move around, so electron density can fluctuate, so small temporary dipoles form, induces dipoles in neighbouring particles
factors affecting vdw
number of electrons (increased chance of dipole formation)
shape of molecule (long chain have more sa for vdw to form)
hydrogen bonding
strongest intermolecular force
form between hydrogen and nitrogen/oxygen/fluorine (most electronegative) as they have a large electronegativity difference
lone pair on N/O/F bonds with H on another molecule
large bp/mp
in ice, molecules arrange themselves in a lattice structure, so H2O molecules are further apart and less dense.
expansion of the octet
3d subshell
there are more than eight electrons around one atom
forms lots of covalent bonds
solid line
bonds are on the plane of the page
solid wedge
bond is coming out of the plane of the page
dotted wedge
projecting back behind the plane of the page
how do you treat double bonds in bond angles?
same as single bonds
how do you treat dative bonds in bond angles?
same as normal bonds
why are ionic substances have high mp and bp
Strong or many or lots of (electrostatic) attractions
Between + and − ions
name of simple covalent crystal
simple molecular
ammonia
NH3
