TOPIC 3 Flashcards
Which elements conduct electricity
Sodium
Magnesium
Aluminium
Describe silicon’s ability to conduct electricity
Semi-conductor
Which element oxide is amphoteric
Aluminium oxide
What does amphoteric mean
Both acidic or basic
Sodium oxide and magnesium oxide produce acidic or basic solution?
Basic
Which element oxides produce an acidic solution
All elements after aluminium
Equation for sulfur trioxide with water
SO3 (g) + H2O (l) - H2SO4 (aq)
Equation for NO2 and water
3NO2 (g) + H20 (l) - 2HNO3 (aq) + NO (g)
Na2O, MgO, Al2O3
IONIC
SiO2, P4O10, SO3, Cl2O7
COVALENT
Describe pH trend of period 3 oxides
Basic to acidic
Describe electron affinity of metals and non-metals
Metals have a low EA because they lose electrons and non-metals have a high EA
Explain the pattern of electron affinity down group 7
Electron affinity decreases down group 7. Less energy is released if further away from nucleus because there is a lot of shielding, weaker force of attraction. Chlorine has the highest electron affinity as fluorine is the smallest atom and so has a high electron density - repels electron that is trying to get into the atom.
Why does oxygen have 2 EA’s
1st EA - exothermic like everything else
2nd - endo - due to electron getting into negative ion and energy needs to be put in to overcome the repulsion
Why are cations smaller than parent?
Because electrons are lost, # of shells decreases. Also, shielding decreases, stronger force of attraction. Nuclear charge increases.
Why are anions larger than parent
Extra electrons increase repulsion, increase shielding, weaker electrostatic force of attraction
Why do transition metals have variable oxidation states
4s and 3d are of similar energy
Their sequential ionisation energies are close together
What are the 3 ferromagnetic metals
IRON
COBALT
NICKEl
What makes a metal paramagnetic
Anything with lone electrons in domains
Diamagnetic?
FULL ELECTRONS in domains
Why is FeCo ligand diamagnetic and not paramagnetic?
use SPECTROCHEMICAL series
CO has the greatest energy difference, d-orbitals split largely
electron comes down
Explain how the colour of solutions containing transition metals can be used to determine their concentration.
Prepare samples of the transition metal ion over a range of known concentrations.
Add a small quantity of a suitable ligand to each in order to identify the colour.
Choose the filter which gives the largest absorbance, and measure the absorbance of each sample using this filter.
Plot a graph of absorbance against concentration.
Take the sample of unknown concentration, add the ligand to intensify the colour, and measure its absorbance using the same filter.
Use the graph to deduce the concentration of the solution.
State three different features of transition metal complexes that cause a change in the
value of ΔE, the energy change between the ground state and the excited state of the
d electrons
Identity of the metal Charge (on the metal) / oxidation state / charge on complex (Identity of the) ligands Co-ordination number / number of ligands Shape
Why are complexes of d-orbitals coloured?
D-orbitals are partially filled
The d-orbitals split into 2 levels due to repulsion of electrons in ligand with electrons in d-orbitals
Energy difference between the 3 low energy d-orbitals and the 2 high energy d-orbitals corresponds to a certain frequency in the visible part of the spectrum
Electron transitions occur from the lower to higher energy level
Complementary colour is seen
What is the coordination number?
The number of lone pairs bonded to the metal ion
Why are complexes of d-orbitals coloured?
D-orbitals are partially filled
The d-orbitals split into 2 levels due to repulsion of electrons in ligand with electrons in d-orbitals as ligand approaches
Energy difference between the 3 low energy d-orbitals and the 2 high energy d-orbitals corresponds to a certain frequency in the visible part of the spectrum
When white light falls on solution, that energy is absorbed
Electron transitions occur from the lower to higher energy level
Complementary colour is seen
Define ligands
Ligands are molecules or ions use lone pair of electrons to form coordinate covalent bonds with a central metal ion
Define polydentate ligands
Polydentate ligands are species that have more than one lone pair of electrons to form coordinate covalent bonds to a central metal ion
Physical properties of metals
High electrical conductivity High melting point High tensile strength Malleable Ductile
Chemical properties of metals
Variable oxidation states
Formation of complex ions
Coloured compounds
Catalytic behaviour
Describe the changes in melting point across period 3
Na to Al = metallic bonding, number of delocalised electrons increases, greater attraction to cations, more energy required to overcome. Also, charge density increases as atoms get smaller
Si = giant covalent, strong covalent bonds require a lot of energy to overcome
S - Ar = simple molecular, weak intermolecular forces, not a lot of energy to overcome
Which elements have the highest electron affinity?
Group 17 elements have incomplete outer energy levels and a high effective nuclear charge of +7 so attracts electrons the most
