2.2.2 bonding and structure

ionic bonding

the electrostatic attraction between positive and negative ions

giant ionic lattice

a 3D structure of a repeating pattern of oppositely charged ions, bonded together by strong ionic bonds

-strong electrostatic attraction between oppositely charged ions
-high temperature needed to provide large amounts of energy to overcome the attraction

high melting+boiling point

-polar water molecules are attracted to the ions on the surface
-ionic bonds are broken so break free from the lattice

high solubility

-solid lattic breaks down so ions are free to move and carry charge

electrical conductivity when aqueous

covalent bond

the strong electrostatic between a shared pair of electrons and the nuclei of the bonded atoms

dative covalent bond

a shared pair of electrons which have both been provided by the same atom

-doesn't shows bond length
-some cana have more than 8 electrons in the outer shel
-most bonds aren't purely ionic or covalent

liminations to the model

average bond enthalpy

a measurement of covalent bond strength

-arrangement minimises repulsion
-electron pairs surround a central atom

electron-pair repulsion theory

2 bond pairs (shape, angle)

linear, 180

3 bond pairs (shape,angle)

trigonal planar, 120

4 bond pairs (shape, angle)

tetrahedral, 109.5

6 bond pairs (shape, angle)

octahedral,90

3 bond pairs, 1 lone pair (shape, angle)

pyramidal, 107

2 bond pairs, 2 lone pairs (shape, angle)

non-linear, 104.5

electronegativity

the ability of an atom to attract the bonding electrons in a covalent bond

polar covalent bond

a molecule with a permenant dipole

polar bond

the bond between dipoles

polar molecules

a molecule with polar bonds that do not cancel due to their direction

2 bond pairs, 1 lone pair (shape, angle)

non-linear 120

5 bond pairs, 0 lone pair (shape, angle)

trigonal bipyramidal 90,120

intermollecular forces

weak interactions between dipoles of different molecules

-the movement of electrons cause an instantaneous dipole which also induces a dipole in the neighbouring molecule
-much weaker than other types of intermolecular forces
-occur between all molecules

London forces (induced dipole-dipole interactions)

bigger atom size = more electrons =

increased strength of dipole interaction

more surface area contacts = more opportunites for induces dipole to occur=

increased strength of dipole interaction

more London forces =

more high melting+boiling points

hydrogen bonding

a permenant dipole-dipole interaction found between molecules (containing O,N,F, H-O,H-F,H-N)

-hydrogen bonds hold water molecules in a lattic structure
-when water freezes 4 H bonds are formed
-the lattice opens up so.......

ice is less dense than water

-water has London forces and hydrogen bonds
-a lot of energy is needed to break the hydrogen bonds so it has....

relatively high melting and boiling points

simple molecular lattice

3D strucutre of molecules bonded by weak intermollecular forces

-weak intermollecular need little energy to break so can be broken at low temperatures (properties of simple molecular lattice)

low melting and boiling points

non-polar molecule w/ non-polar solvent
-intermolecular forces form between the molecules and the solvent
-weakens the simple molecular lattice which break

soluble

non-polar molecule w/ polar solvent
-little attraction between the lattice and solvent molecules
-can break the bonds in some places but mostly is not broken

soluble/insoluble

polar molecule w/ non-polar solvent
-dipole-dipole interactions in the molecules don't react well with the solvent
-however there are some non-polar regions so some parts dissolve

soluble/insoluble

polar molecule w/ non-polar solvent
-polar solute attracts the polar solvent so dissolve

soluble

bigger molecule=

more soluble

-no mobile charged particles in simple molecular structures
-nothing to conduct electricity and complete circuit
so...

electrical non-conductors