BONDING Flashcards
Crystals
crystals are solid held together by force of attraction.
forces of attraction includes?
intermolecular forces - london forces, dipole dipole forces and hydrogen bonds.
- bonding - ionic, covalent and metallic bonding.
ionic bonding
ionic bonding is the strong electrostatic force of attraction between oppositely charged ions.
ionic structure
the ionic structure exists in a lattice ( regular pattern of oppositely charged ions). ions are held together by strong electrostatic force of attraction. eg is sodium chloride.
why do ionic compounds have ahigh melting point?
ionic compounds have strong electrostatic attraction between oppositely charged ions. therefore a lot of energy is required to break the strong bonds.
why can ionic structures conduct electricity ?
when dissolved in water or molten, ionic lattice break into ions. ions are free to move and able to carry charge which allows ionic structure to conduct electricity in even aqueous or molten state.
metallic bonding
metallic bonding is the strong electrostatic attraction between positively charged ions and negatively charged delocalised electrons in a lattice.
metal ions
metal ions are held in a regular lattice. example is magnesium.
why does metallic bonding have high melting points
becaus eof the strong electrostatic attraction between positive ions and delocalised sea of electrons . the more number of delocalised electrons = the stronger the bonding = the higher the melting point.
conductivity in metals
delocalised electrons can pass kinetic energy to each other,making metals good thermal conductors. metals are a good electricty conductor because the delocalised electrons can move and carry current.
solubility of metals
metals are insoluble except in some liquids because of the strength of the metallic bonds.
covalent bonding
covalent bonding involves strong electrostatic attraction between shared pair of electrons and the nuclei of the bonded atom.
it usually occurs between non metals. and is represented by dot and cross diagrams.
why do metals want to have a full shell?
to increase stability and decrease reactivity.
single covalent bonding
single covalent bonding involves one shared pair of electrons. example h20 where hydrpgen and oxygen share one pair of shared electrons on both sides leading to a full outer shell.
multiple covalent bonding
involves more than one shared pair of electrons. involves double bonds and triple bonds. oxygen is an example of double bond as it shares two shared pairs of electrons to gain a full outer shell and exanple of triple bonds is nitrogen.
dative covalent bonds or co ordinate bonds.
one atom donates both of the electrons in a covalent bond. eg ammonium ion or nh4 +.
structures of the covalent compounds
- simple molecular lattice
- giant covalent latttice.
simple molecular lattice
- made up of simple molecules.
- exists as a lattice in solid state.
- atoms held together by strong covalent bonds within molecules.
- weak intermolecular forces of attraction between the molecules.
properties
- low mp and bp = because of the weak intermolecular forces between the molecules.
- no electrical conductivity because there is no charged particle.
- only soluble in non polar solvents.
giant covalent mplecule
- atoms are joined to adjacent atoms by strong covalent bonds.
- giant lattice is formed.
- example : graphite, diamond and silica
properties of giant covalent structures
1.high mp and bp because of the presence of the strong covalent bonds. more energy required to break the bonds.
2. insoluble in polar and non polar solvents because the strong covalent bonds are not disrupted by any solution.
3. no electrical conductivity as there is no charge in the electrons except graphite.
exception : graphite
between the layers of lattice, delocalised electrons are able to move when voltage is applied. electrons are able to move freely parallel to the layers.
types of giant covalent substance
diamond = high mp, very hard, insoluble and non conductor.
graphite = high mp, soft and slippery, insoluble and electrical conductor.
silica = high mp, hard , insoluble and non conductor.
