topic 2 - chemical bonding Flashcards
hydrogen bond
-element that has to be more electronegative than hydrogen
-electrostatic attraction between hydrogen atoms bonded to small strongly electronegative atoms and the -lone pair of electrons on there
-strong bonds
trigonal bipyramidal
5 bond
0 lone pairs
e.g PCl5
tetrahedral
4 bond
0 lone pairs
octahedral
6 bond
0 lone
triagonal planar
3 bond
0 lone
triagonal pyramidal
3 bond pairs
1 lone
e.g PCl3
linear
2 bond
0 lone
v-shaped
2 bond
1 lone
ionic compounds properties
high melting point
-strong forces of attraction
brittle
-if stress is applied the layers can slide over each other and now same charged ions repel
conductor
-no free flowing ions in solid but in liquid ions are free moving so can move with the charge
soluble
energy needed can be suplied by hydration because of polarity
ionic bonding
giant lattice
strong electrostatic forces between anions and cations
strong electrostatic attraction between two oppositely charged ions
stregnth of ionic bonds
size of ions
-smaller -> more energy
covalent bonding
non metals
share outer electrons to become more stable
strong electrostatic attraction between 2 nuclei and a bonding pair of shared electrons
types of covalent bonding
sigma is stronger as there is a good overlap of s orbitals where as there is a weaker overlap of p orbitals
larger atomic radius -weaker bond
more sheilding
further from nucleus
more bonds - stronger bonds
electronegativity
ability of an atom to attract a bonding pair of electrons
decreases down a group - increase in shells + sheilding
increase across a period - charge increases
larger difference in electronegativity means stronger bonds
polar covalent bonds
if the two elements have the same elctronegativities the covalent bond will be equal
if they are different the density of the covalent bond will be different
the change slightly differs so it becomes a polar molecule
discrite molecules
covalent molecule in which forces are weak
dative bond
when an empty orbital atom overlaps with an orbital containing a non bonding pair of electrons of another atom
london forces
-van der waal
-weak bonds
uneven distribution of electrons
forms temporary dipoles
this can induce dipoles in others
if more branched london forces weaker as more surface area
electron pair repulsion theory
the shape of a molecule or ion is caused by the repulsion between the pairs of electrons, both bonded and lone
the electron pairs arrange themselves to minimize repulsion
lone-lone>lone-bond>bond-bond
repulsion
dipole
seperation of charge
polar
if the dipoles in a molecule reinforce each other the molecule has an overall dipole
non polar
if the dipoles cancel each other out the molecule will have no dipole
permenant dipole
not always a favourable interaction
very weak- weaker than induced
metalic bonding properties
high melting temperatures
good conductivity
malleable
ductile
low ionisation energys
delocalised electrons
giant lattice
