A summary of topic 15, organised so the notes are easy to understand. The notes are on slides, so they can be printed out and used as revision cards or posters, for revision on the go. The notes cross-reference the specification so it is easy to see where each bit of information has come from. They...
Transition metals Variable oxidation states
= d-block elements that can form one or more stable ions - Most transition metals can form multiple stable ions
with incompletely filled d-orbitals - Vanadium has 4 stable oxidation states
Characteristics ⤷ Vanadium (II) = V^2+
- High MPTs & BPTs ⤷ Vanadium (III) = V^3+
- Good conductors of heat & electricity ⤷ Vanadium (IV) = VO^2+
- Hard ⤷ Vanadium (V) = VO2^+
- Act as catalysts To form a compound or complex containing an ion with a certain
- Form coloured ions & compounds oxidation number:
- Form ions w/ different oxidation states The energy given out when the ion forms a compound or complex
- Form ions w/ incomplete d-orbitals needs to be greater
Electron configurations Than the energy required to remove the outer electrons (ionisation
- 4s filled before 3d energy)
- 3d orbitals occupied singly, the e-’s only double up - entropy also contributes to this
when they have to (repulsion ∴ unfavourable) Trends in oxidation states
Chromium = one electron in 4s & 3d orbitals (↑ stable to
have 1e- in each orbital)
- [Ar] 3d^5 4s^1 From Ti to Mn:
Copper = full 3d orbital, only one e- in 4s - The highest common oxidation number increases
- [Ar] 3d^10 4s^1 - All 4s & 3d electrons involved in bonding as there aren't that
Formation of ions many of them
(4s electrons are removed first due to slightly higher energy From Fe to Cu:
that 3d) - The high oxidation states are less common
Copper = [Ar] 4s^1 3d^10 - The nuclear charge ↑ so the electrons are more strongly held
- Cu^+ = [Ar] 3d^10 and are less likely to be involved in bonding
- Cu^2+ = [Ar] 3d^9 Why variable oxidation states?
Titanium = [Ar] 4s^2 3d^2 - Transition metals form ions by losing electrons from the 4s &
- Ti^2+ = [Ar] 3d^2 3d subshells
- Ti^3+ = [Ar] 3d^1 - Very similar energy levels so it takes a similar amount of
Scandium & Zinc energy to remove an electron from each
Sc = [Ar] 4s^2 3d^1 Sc & Zn don’t have a - There is not a large increase between ionisation energies of
- Sc^3+ = [Ar] partially filled d-orbital when removing successive electrons so multiple electrons can be
Zn = [Ar] 4s^2 3d^10 they are stable ions ∴ not removed
- Zn^2+ = [Ar] 3d^10 transition metals
, Complex ions Complex ions - charge
= metal ions surrounded by dative covalent bonded ligands - The overall charge on the complex ion is its oxidation number
Ligand = an atom, ion or molecule that donates a pair of - Written outside the square brackets
electrons to a central metal atom or ion. A ligand must have - Can be used to work out the oxidation state of the metal
at least one lone pair of electrons (to form a dative covalent - Oxidation number of metal = total - sum of ligands
bond) [Fe(H2O)6]^2+ Fe = 2+
- Monodentate
No charge
= one lone pair of electrons [Fe(CN)6]^4- Fe = 2+
⤷NoHcharge
2O (can 2 lone pairs but can only form 1) Number of ligands
⤷ :NH3, :Cl-, :OH-, :CN- Coordination number = number of dative covalent (coordinate)
- Bidentate = two lone pairs No charge bonds formed with the central metal ion
⤷ 1,2-diaminoethane (NH2CH2CH2NH2) - Usually 4 - 6
- Multidentate = more than two lone pairs - Small ligands (e.g. H2O & OH-) = 6 can fit around central
⤷ EDTA^4- (six lone pairs) metal ion
⤷ COO- (4 lone pairs) - Large ligands (e.g. Cl-) = only 4 can fit around the central
Ligand Formula Charge Name in complex
metal ion
- Ligands do not have to be the same
Water HO
2 0 Aqua - The bonding electrons in the dative covalent bonds repel
each other, therefore the ligands need to be as far away from
Hydroxide OH- -1 Hydroxo
each other as possible (min repulsion, max separation)
Ammonia NH 3 0 Ammine - Causes complexes with different coordination numbers to
have different shapes
Chlorine Cl- -1 Chloro Coordination number 6 (6 fold coordination)
Shape = octahedral
Fluorine F- -1 Fluoro
Bond angle = 90°
Cyanide CN- -1 Cyano Examples = [Fe(H2O)6]^2+ [Fe(H2O)6]^3+ [Cu(H2O)6]^2+
[Co(NH3)6]^3+
Naming complexes Hexa = 6
1. Number of ligands →→→→→→→→→→→→→→ Tetra = 4
2. Name of ligand Tri = 3
- If two different ligands, do in alphabetical order Di = 2
1. Name of the metal ion Mono = 1
- Metal ion becomes ‘ate’ if it’s part of a -vely charged
complex
- Iron → ferrate when -ve
- Copper → cuprate when -ve
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