transition metals

[Cu(H2O)6]2+, from copper sulfate.5H2O (s)

pale blue

vandium 2+ in solution

Violer

Vandium 3+ in solution

Green

VO⁺

yellow

Cr³⁺ (2)

Violet when surrounded by 6H2O, but normally substituted to be green

VO^{2+ (V is charge 4+)}

blue

Cr₂ O₇ ^2-

Orange

Mn²⁺

light pink

MnO₄ ^2-

green

MnO₄ ^-

Purple

Fe 2+ in solution

light green

Fe 3+ in solution

yellow

Co 2+ in solution

pink

Ni 2+ in solution

green

Cu 2+ in solution

blue

Ti 2+ in solution

violet

Ti 3+ in solution

purple

When OH- or NH3 - is added to aqueous solution of Cu2+

pale blue precipitate of cu(OH)2(H2O)4 (s)

When OH- or NH3 - is added to aqueous solution of Fe2+

Fe(OH)2 (s) dark green / dirty green precipitate

When OH- or NH3 - is added to aqueous solution of Fe3+

Fe(OH)3 (s), orange-brown precipitate

When OH- or NH3 - is added to aqueous solution of Mn2+

pale pink / pale brown precipitate of Mn(OH)2

When OH- or NH3 - is added to aqueous solution of Cr3+

dark green precipitate Cr(OH)3

Adding excess of NH3 to Cu2+

dark blue solution, [Cu(NH3)4(H2O2)2] 2+

excess HCL to Cu2+

CuCl4 2-, yellow

Reduction of Cu2+ with I-

white precipitate (CuI) and brown I2

Cu colour

brown solid

CoCl2.6H2O(s) plus water and excess HCl

CoCl4 2–, blue

excess NH3 to Cr 2+(aq)

[Cr(NH3)6] 3+, purple solution

MnO4 – /Fe2+ Mn2+/Fe3+

purple (MnO4 – ) to pale pink (Mn2+) (in titrations, so dilute that it is practically colourless)

transition element definition

d-block element that can form atleast one stable ion with a partially filled (incomplete) d-subshell

why do orbitals fill up singly then double up

electrons repel eachother

Which d-block elements aren’t transition elements

scandium and zinc

max amount of electrons d subshell holds

10

What’s so special about the electron configuration of copper and chromium?

electron from 4s orbital moves into the 3d orbital to create a more stable half full or full 3d subshell respectively

Why aren’t scandium and zinc transition elements

scandium only forms the stable ion Sc³⁺ which has an empty subshell

zinc only forms he stable ion Zn@+ which has a full d subshell

Why do we always remove 4s orbitals before 3d (2)

electrons are further away from nucleus in 4s

higher energy, less attraction to nucleus

3 properties of transition elements

1. variable oxidative states

2. form coloured ions in solution

3. can be used as catalysts

explain the variable oxidative states of transition elements (3)

• electrons sit in 4s and 3d energy levels, which are very close

• electrons can transition readily between 4s and 3d orbitals

• electrons ae gained and lost using a similar amount of energy when they form ions

• first ionisation energies are very small, small amount of energy to remove electrons

explain how transition elements can be good catalysts, and why that’s good (3)

• transition metals have variable oxidative states so they are good catalysts by receiving and losing some electrons in the 4s/4d orbitals to speed up reactions

• have surfaces that allow substances to adsorb to the surface which lowers Ea of reaction

• products are made faster at lower temp, saving energy and money, better for the environment

risks of using t metals as catalysts (2)

• long term copper exposure: damage to liver. ring of copper in eye is sign of copper poisoning

• long term exposure to manganese causes psychiatric issues and physical tremors

Cu2+ is used as a catalyst for…

reaction of Zn with acids

`MnO2 is used as a catalyst

decomposition of H2O2

Complex meaning

transition metal forms a complex of a central metal surrounded by ligands. held together by coordinate / dative bonds

ligand definition and examples

molecule or ion with lone electron pair that is able to form a dative (coordinate) bond to the central metal ion by donation of this electron pair

• Cl-, H2O, NH3

Monodentate ligand definition and examples

form one coordinate bond, eg. H2O, Cl-, NH3

bidentate ligand definition and examples

form two coordinate bonds

eg. NH2CH2CH2NH2

dative / coordinate bond definition

covalent bond where both shared electrons in the bond come from the same atom

Excess OH- to Cr3+

green solution

Coordination number

total number of coordinate bonds formed with the central metal ion

why are transition metals identifiable by their colour (4)

colour depends on coordination number, type of ligand bonded, and oxidation state

colour arises because of how substances absorb and refect light

ligands cause d orbitals to split, so electrons exist in slightly higher energy level in excitated state

change of energy between these states corresponds to specific wabelength and frequency of light

why can some ions be colourless

• no available electrons

• so no excitation of electrons so no different energy levels

tetrahederal complex bond angle

109.5

what two transition elements have a square planar shape with a bond angle of 90

platinum and nickel complexes

describe cisplatin (6)

• cis isomer of square planar complex of platinum

• chlorine atoms are on same side

• cancer therapy drug

• target components of cells that are chiral

• onle one single isomer will work to cure disease

• causes serious side effects eg. hair loss so must be used in small amounts

Are Cl- or H2O and NH3 ligands larger

Cl- ligands are larger

Coordination number of Cl- ligands is always

4

Describe the chelate effect (3)

• bidentate / multidentate ligand will substitute monodentate ligand

• because there will be more particles / mols on right hand side, so entropy is positive (higher disorder between particles)

• entropy is positive, free energy is negative, so feasible.

enthalpy change of ligand substitution reactions (2)

• very small

• bonds being formed are very similar to bonds being broken

With aqueous sodium hydroxide, metal aqua ions react as…

acids

order of tests for anions

• carbonate

• sulfate

• hallide

testing for carbonate(CO3 2-) and hydrogencarbonate (HCO3 - )

• when acid such as HCL is added, substance containing carbonate ions will fizz and CO2 gas is given off

• collect gas and bubble through limewater which will turn cloudy to confirm identity

test for sulfate ions

• uses acidified BaCl2, which reacts to form a white precipitate of barium sulfate

tesing for hallide ions

1. acidified nitrate with ethanol as solvent: Cl - white precipitate, Br- cream precipitate, I- yellow precipitate

2. dilute NH3: Cl- precipitate dissolves

3. onc. NH3: Cl- and Br- precipitate dissolves

test for ammonium (NH4+)

• add NaOH and gently warm

• forms ammonia gas, which is basic

• hold red damp litmus paper over substance. blue = ammonium

[Cu(H2O)6] 2+ colour

Pale blue

Cu(OH)2 (s) colour

Pals blue precipitate

[Cu(NH3)4(H2O)2 ]2+ Colour

Dark blue

CuCl4

2–

Yellow

Cu+

White precipitate (CuI) and brown I2

Cu2+ / Cu colour

Disproportionately of Cu+

Brown solid (Cu) and blue solution ( CuSO4)

CoCl4

2–

from CoCl2.6H2O(s) plus

water and excess HCl

Blue

[Cr(H2O)6]3+

from KCr(SO4)2.12H2O(s)

(heat green)

Due to impurities, it is

common for Cr(III) to

appear green in solution

If precipitate from silver nitrate dissolves in dilute ammonia it’s

Chloride

If precipitate from silver nitrate dissolves in concentrated ammonia it’s

Bromine

If precipitate from silver nitrate does not dissolve in concentrated ammonia it’s

Iodide