d-block elements Flashcards
Where are the d-block elements located?
Between group 2 and group 3.
What is the highest energy in d-block elements? So?
The 3d sub-shell, and so electrons are added to the 3d orbitals.
What are the 4 physical properties of d-block elements?
- High melting points.
- High boiling points.
- Shiny in appearance.
- Conduct electricity and heat.
What are 4 uses of d-block elements?
- Production of tools.
- Electrical cables.
- Aerospace industry.
- Joint replacement/cosmetic dentistry.
What are the electron configurations like in d-block elements? E.g.?
The 4s sub-shell is filled before the 3d sub-shell as it occupies a lower energy.
- E.g. 1s2 2s2 2p6 3s2 3p6 3d3 4s2.
Why don’t chromium and copper fill the usual electron configurations?
Because of stability: a half-filled d5 sub-shell and a fully filled d10 sub-shell gives more stability to atoms of chromium and copper.
What are the electron configurations of chromium and copper?
- Chromium: 1s2 2s2 2p6 3s2 3p6 3d5 4s1.
- Copper: 1s2 2s2 2p6 3s2 3p6 3d10 4s2.
What is the rule for forming positive ions of d-block elements?
The 4s electrons are removed before any of the 3rd electrons are removed.
Overall, what is the rule for a d-block element forming an atom and a d-block element forming an ion?
- When forming an atom, the 4s orbital fills before the 3d orbitals.
- When forming an ion, the 4s orbital empties before the 3d orbitals.
What is a transition element? Although?
D-block elements that form at least one ion with a partially filled d-orbital (although, scandium and zinc are d-block elements, but they do not match this definition and so are not classified as transition elements.
Why is scandium not classified as a transition element?
Because the ion it forms of Sc3+ doesn’t create a partially filled d-orbital, only empty d-orbitals.
Why is zinc not classified as a transition element?
Because the ion it forms of Zn2+ has fully filled d-orbitals, not partially filled ones.
What are the 3 characteristic properties of transition metals that are different from other metals?
- They form compounds in which the transition element has different oxidation states.
- They form coloured compounds.
- The elements and their compounds can act as catalysts.
What compounds do transition elements form? E.g.?
Ones with more than one oxidation state, e.g. iron forms 2 chlorides - iron (II) chloride and iron (III) chlorides.
What is the trend in number of oxidation states across the transition elements?
Increase as goes along, until it reaches manganese where it then decreases.
What is always the oxidation number of the compounds formed from transition elements? Why?
-2+ because 2 electrons are lost.
What does each oxidation state usually have?
A characteristic colour.
What is a species containing a transition elements in its highest oxidation state often?
A strong oxidising agent.
What are 4 examples of colours of compounds and ions of transition elements?
- Potassium dichromate (VI): bright orange.
- Colbalt (II) chloride: pink/purple.
- Nickel (II) sulfate: green.
- Hydrated copper (II) sulfate: blue.
What do the solid compounds dissolved in water produce?
A coloured solution.
What is the colour of the solution linked to?
The partially filled d-orbitals of the transition metal ion.
How can the colour of a solution vary?
With different oxidation states.
What are 2 examples of how different oxidation states can form different coloured solutions?
- Iron:
- Fe2+ = pale green.
- Fe3+ = yellow. - Chromium:
- Cr (III): green.
- Cr (VI): yellow or orange.
What is a catalyst? How does it work?
A substance that increases the rate of a chemical reaction without itself changing by providing an alternative reaction pathway with a lower activation energy.
What are 4 processes in which transition metals and their compounds being catalysts is important?
- Haber process in the manufacture of ammonia from nitrogen and hydrogen. Catalysed by a finely divided iron catalyst.
- Contact process in production of sulfur trioxide from the oxidation of sulfur dioxide. Catalysed by vanadium (V) oxide, V2O5.
- Hydrogenation of vegetable fats in the manufacture of margarine. Uses nickel as the catalyst.
- The catalytic decomposition of hydrogen peroxide forming oxygen. Uses manganese (IV) oxide, MnO2 as the catalyst.
What are all the above processes an example of? Why?
Heterogeneous catalysis, as the catalyst is in a different state to the reactants.
What are homogeneous catalysts?
Where the catalyst is in the same physical state as the reactants.
What is an example of a reaction that uses homogeneous catalysts? Equation?
- The reaction between iodide ions and peroxodisulfate ions, S2O8^2- and is catalysed by Fe2+ (aq), with all of the reactants and catalyst in aqueous solution.
- S2O8^2- (aq) + 2I- (aq) = 2SO4^2- (aq) + I2 (aq).
What happens when you use a trace of starch in the reaction with S2O8^-2 ions?
A blue-black colour forms showing the formation of iodine.
What happens if you then repeat this S2O8^2- experiment with a bit of Fe2+ (aq) added? Shows?
The blue-black solution forms quicker, showing the catalytic action of the transition metal ion.
