4.1 - Ionic Bonds
4.2 - covalent bonding
4.3 - covalent bonding 2
4.4 - intermolecular forces
4.5 - metallic bonding
100
What is ionic bond?
Electrostatic attraction between oppositely charged ions.
100
Definition of covalent bonding
A covalent bond is the electrostatic attraction between positively charged nuclei and shared pairs of bonding electrons
100
what is the octect rule
most stable arrangement for an atom is to have eight electrons in its outermost energy level with the electron configuration of a noble gas.
total of eight electrons in the valence shells
100
Weakest type of intermolecular forces?
London dispersion forces (London forces)
100
Alloy definition?
Alloys are homogeneous mixtures composed of two or more metals or a metal and a non-metal
200
Examples of cations. name 3
H+. Na+ etc
200
Draw a lewis structure of Cl2
200
exceptions to the octet rule
According to the octet rule, atoms bond to gain a full outer shell of eight electrons. However, there are exceptions:
Hydrogen is stable with only two electrons in its outer shell.
Atoms such as boron, beryllium and aluminium (in compounds) are stable with fewer than eight electrons in their outer shell.
Atoms in period three and higher, such as sulfur, can form expanded octets with up to twelve electrons in their valence shell.
200
Describe a dipole-dipole force
Only between polar molecules
permanent dipole
Example: HCl
permanent dipole
difference in electronegativity between hydrogen and chlorine
Hydrogen: lower electronegativity value -> partial positive charge
Chlorine: higher electronegativity value -> partial negative charge
Force of attraction between partial negative charge of one chlorine atom of one HCl molecule and the partial positive charge of hydrogen atom on another HCl molecule
200
What do the Strength of metallic bond depends on?
Strength of metallic bond depends on :
Charge on the metal ion
Ionic radius of the metal ion
300
Examples of polyatomic ions? Name 5.
OH-, NO3-, HCO3-, SO42-, CO32-, PO43-, NH4+, etc
300
whats the bond order for single, double, and triple bond?
Single bonds have a bond order of 1, double bonds have a bond order of 2 and triple bonds a bond order of 3
300
What is the VSEPR theory?
Valence shell electron pair repulsion theory (VSEPR)
predict the shapes of molecules
electron pairs in molecules repel each other
Electron pairs will orientate themselves as far away from each other as possible
molecule will adopt the shape that minimises the repulsion between the electron pairs.
300
Three types of intermolecular forces?
Three types of intermolecular forces
1) London dispersion forces
2) dipole-dipole forces
3) hydrogen bonding
300
What are the unique properties of metals?
Metals are:
good conductors of heat and electricity,
ductile (can be made into wires),
malleable (can be bent into shape) and
shiny when polished.
400
Describe the structure of ionic compounds.
Ions are arranged in a regular crystalline structure
Lattice structure
Non-directional
400
how do you determine bond polarity?
electronegativity is the measure of the attraction of an atom for a shared pair of bonding electrons (eg water)
difference in electronegativity determines the type of bonding that takes place between atoms
400
What are the resonance structures of carbonate?
400
Describe and draw out hydrogen bonding
Hydrogen bonding occurs between molecules that have an electronegative nitrogen, oxygen or fluorine atom directly bonded to a hydrogen atom
stronger type of dipole–dipole attraction
responsible for the high boiling point of water
Hydrogen bonds exist between water molecules
between the lone pairs of electrons on the oxygen atom and the hydrogen atom on a nearby water molecule
400
Describe the metallic structure
Only in metal ions
Valence electrons are free to move throughout the metallic structure:
Delocalised electrons
Sea of delocalised electrons
Metal atoms:
Ionised
Positive
Arranged in lattice structure
500
Describe electrical conductivity
Depends on the presence of mobile ions
Ionic compounds do not conduct electricity when solid because the ions are held in fixed positions in the lattice structure.
Melted (molten) or dissolved: ions are free to move and carry an electrical current
500
arrange the types of bonding (ionic, polar covalent, and no-polar bonding) according to the difference in electronegativity between the bonded atoms. (spectrum of bonding)
not a strict separation between ionic and covalent bonds
gradual shift from non-polar covalent bonds to polar covalent bonds to ionic bonds depending on the difference in electronegativity between the bonded atoms
500
What are the factors of molecular polarity?
Two factors:
Presence of polar bonds within the molecule
Molecular geometry of the molecule
500
Evidence for hydrogen bonding - why is there a large decrease in boiling point from H2O to H2S and then an increase from H2S to H2Te?
- large decrease in boiling point between H2O and H2S is due to the fact that water is able to form strong hydrogen bonds between its molecules
gradual increase from H2S to H2Te is caused by the increase in molar mass
stronger London dispersion forces between the molecules
Polar molecules: difference in electronegativity between the atoms in the molecule and the bent molecular geometry
500
Describe the electrical conductivity of metallic bonding.
The presence of delocalised electrons in the metallic lattice accounts for the high thermal and electrical conductivity of metals.
When potential difference (voltage) is applied:
direction is imposed on the movement of the delocalised electrons
repelled from the negative electrode
move towards the positive electrode
orderly flow of delocalised electrons in a given direction constitutes the flow of an electric current