U1- Bonding and shapes Flashcards
metallic bond
a lattice of positively charged ions (cations) surrounded by free-moving ‘delocalised’electrons
metals are good conductors of heat because
the fact that they have delocalised electrons flowing through the lattice which can collide with the metal ions and pass on heat energy
metals are good conductors of electricity because
sea of delocalised electrons flowing through the lattice are free to move and carry electrical charge
metals are malleable and ductile because
the fact that the attraction between the metal lattice and delocalised electrons can take a fair amount of force before the lattice breaks and so it maintains its properties whilst changing shape
metals generally have high melting and boiling points because
the fact that the electrostatic force of attraction between the metals cations and the delocalised electrons is strong and requires a lot of energy to break
alloys
combinations of two or more metals
alloys vs pure metals
because when two or more metals form an alloy, the arrangement of the ions is disturbed tf alloys are:
harder than pure metals
less malleable
poorer conductors
metals are lustrous because
delocalised electrons form a barrier to reflect the light from the surface
galvanising/ galvanisation
the process of applying a protective zinc coating to steel or iron to prevent rusting
protects iron or steel by preventing corrosive substances from reaching the underlying steel/iron and protects iron by corroding first
extraction of iron
1) coke reacts in oxygen to form carbon dioxide
C + O2 –> CO2
2) CO2 is reduced by carbon to form carbon monoxide
CO2 + C –> 2CO
3) CO reduces iron oxide to form iron
Fe2O3 + 3CO –> 2Fe + 3CO2
4) Limestone breaks down in heat calcium oxide ad carbon dioxide
CaCO3 –> CaO + CO2
5) calcium oxide reacts with sand to form slag
CaO + SiO2 –> CaSiO3
extraction of aluminium
1) Bauxite is purified and crushed then dissolved in NaOH
2) Dissolved in cryolite (Na3AlF6) as this lowers the boiling point to 1000C compared to AL2O3 2040C boiling point
3) At cathode: Al3+ + 3e –> Al (red)
4) At anode: 2O2 –> O2 + 4e (ox)
5) Then at anode (as anode made of C):
C + O2 –> CO2
so anode needs replacing
formula unit
smallest whole number ratio of atoms in an ionic compound
why do atoms gain or lose electrons?
to form a stable configuration
polyatomic ions symbol for: acetate (ethanoate) permanganate cyanide chromate dichromate peroxide
CH3COO-1 MnO4-1 CN-1 CrO4-2 Cr2O7-2 H2O2
*molecular formular
smallest unit of a substrate that retains the chemical and physical properties of a substrate.
they have a known formula
2 or > non metals
covalent bond
shared pair of electrons between. two non-metallic atoms
dative covalent bond
covalent bond in which both of the shared electrons are contributed by one atom only
eg NH4
valence structure vs lewis structure
valence = lone pairs have dots, bonds have lines lewis = all dots
octet rule
covalent bonds form so that the bonded atoms obtain a noble gas configuration generally having 8 e- in outer shell
(hw) not always true eg boron or sulfur
Valence Shell Electron Pair Repulsion (VSEPR) Theory
electron pairs within a molecule have a repulsive effect on each other
shape of a molecule is determined by the number of electron pairs surrounding the central atom
shape affects melting point, boiling point, hardness and solubility
(double bond pair behaves as a single region of electron density)
(lone pair is more repulsive than bonding pair)
shape: linear
4 total e-
2 bp
0lp
OR
3 lp
shape: trigonal planar
6 total e-
3 bp
0lp
shape: tetrahedral
8 total e-
4 bp
0 lp
shape: trigonal bipyramidal
10 total e-
5 bp
0 lp
