Transition Elements Flashcards
How do you work out the electronic configuration of atoms and ions in the d-block of the periodic table?
4s subshell fills before 3d subshell
From Sc-Zn, the 3d subshell is being filled
Exceptions are chromium, Cr which has (Ar)4s(1)3d(5) and copper, Cu which has (Ar)4s(1)3d(10)
When making ions, the 4s electrons are lost first
Define transition elements
D-block elements that form a stable ion with an incomplete d sub-shell. Note: scandium and zinc are d block elements but are not transition elements
What are the properties of transition metals?
Exist in more than 1 oxidation state for each element in its compounds
Form coloured ions
Act as catalysts as elements or in compounds
How can transition elements exist in more than one oxidation state?
All form 2+ ions by losing the 4s electrons
As 4s and 3d subshells are so similar in energy level, the 3d electrons can also be lost and a stable ion formed. The highest oxidation states formed are +6 in Chromium and +7 in manganate. These are powerful oxidising agents.
What colour are the oxidation states of Vanadium?
+2: lilac
+3: green
+4: blue
+5: yellow
What colour are the oxidation states of Chromium?
+2: dark blue
+3: green
+4 and +5: colourless
+6: orange
What colour are the oxidation states of Manganese?
+2: pale pink
+3 - +6: colourless
+7: purple
What colour are the oxidation states of Iron?
+2: pale green
+3: pale yellow
+4 - +6: colourless
What colour are the oxidation states of Cobalt?
+2: pink
+3: olive green
+4 and +5: colourless
What colour are the oxidation states of Copper?
+2: blue
+3: colourless
How do transition metals act as catalysts?
Either - provide a surface for the reaction to take place on: adsorbtion of reactants onto the surface of the metal and held in place while a reaction occurs
Or - change in oxidation states by gain/loss of electrons, forming intermediates as part of a chemical pathway with a lower activation energy
What are the observations and the ionic equation for cobalt ions reacting with NaOH?
Observations: pink solution containing Co(2+) forms blue precipitate that turns beige in the presence of air
Equation: Co(2+)aq + 2OH(-)aq -> Co(OH)2s
What are the observations and the ionic equation for copper ions reacting with NaOH?
Observations: pale blue solution containing Cu(2+) forms a pale blue precipitate
Equation: Cu(2+)aq + 2OH(-)aq -> Cu(OH)2s
What are the observations and the ionic equation for iron (II) ions reacting with NaOH?
Observations: pale green solution containing Fe(2+) forms a green precipitate that turns rusty brown in presence of air (Fe(2+) oxidised to Fe(3+))
Equation: Fe(2+)aq + 2OH(-)aq -> Fe(OH)2s
What are the observations and the ionic equation for iron (III) ions reacting with NaOH?
Observations: pale yellow solution containing Fe(3+) forms a rusty brown precipitate
Equation: Fe(3+)aq + 3OH(-)aq -> Fe(OH)3s
Define ligand
A molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond
Define complex ion
A transition metal ion bonded to one or more ligands by coordinate bonds
Define coordination number
The total number of coordinate bonds formed between a central metal ion and its ligands
What shape does a transition metal that has formed 6 coordinate bonds take?
Octahedral, with 90* between each bond. An example of one like this would be (Fe(H2O)6)2+
Define bidentate ligand
A ligand that can donate 2 lone pairs of electrons to the central metal ion, forming 2 coordinate bonds. An example is ethane-1,2-diamine (en) which is NH(2)CH(2)CH(2)NH(2), where each nitrogen atom donates a pair of electrons
What kinds of stereoisomerism to transition metals show?
Cis-trans isomerism: when have 2 different ligands and they are either together or opposite each other
Optical isomers: can occur when have 3 bidentate ligands, or the cis version from above
How is cis-platin work as an anticancer drug?
Its the cis version of (PtCl(2)NH3(2))
Cis-platin binds to DNA of fast growing cancer cells, altering the DNA, preventing the cells from reproducing due to changes in the DNA structure. The cell’s repair mechanism then destroys the cancerous cell.
What is ligand substitution?
The process in which one ligand in a complex ion is replaced by another ligand
What are the observations and the equation when (Cu(H2O)6)2+ is converted into (Cu(NH3)4(H2O)2)2+?
Observations: pale blue solution forms a pale blue precipitate on addition of a small amount of ammonia (Cu(OH)2) which dissolves on addition of excess ammonia forming a deep blue solution
Equation: [Cu(H2O)6]2+(aq) + 4NH3(aq) [Cu(NH3)4(H2O)2]2+(aq) + 4H2O (l) Note: equilibrium reaction
