Transition elements Flashcards
What is a transition element?
an element that forms one of more stable ions with a partially filled d sub-shell
How many electrons can a d sub-shell hold?
10
Which 2 elements in period 4 of the transition elements are not actually transition elements?
zinc and scandium
Why is zinc not a transition element?
is only forms Zn2+ by the loss of two 4s electrons which gives the configuration 3p6 3d10 - so its ion has a fully filled 3d subshell
Why is scandium not a transition element?
Sc only forms Sc3+ as a stable ion by loosing two 4s electrons which gives the configuration 3s2 3p6 so it has an empy 3d sub-shell
Which orbital fills up first when forming an atom of a transition element?
4s orbital
Which orbital empties first when forming an ion of a transition element?
4s
What are the 2 exceptions to the 4s orbital filling up first?
Copper and Chromium
What is the electron configuration of chromium? (3d and 4s)
3d 5, 4s 1
What is the electron configuration of copper (3d and 4s) ?
3d 10, 4s 1
What are the 3 properties of transition metals?
- variable oxidation states in compounds
- metals and compounds can act as catalysts
- they form coloured compounds
Why can transition metals form variable oxidation states?
the energies of 4s and 3d electrons are very similar, these elements can lose variour number of electrons when they form stable compounds
How does a catalyst work?
provides an alternative pathway for a reaction with a lower activation energy thereby speeding up the reaction
What 2 reactions does iron catalyse?
the haber process
N2 + 3 H2 == 2NH3
acts as a halogen carrier in electrophilic substitutions
What reaction does vanadium (V) oxide (V2O5) catalyse?
the contact process
2 SO2 + O2 == 2 SO3
What reaction is catalysed by Ni?
hydrogenation of alkenes
What reaction does Pt catalyse?
hydrogenation of nitriles
What reaction does manganese (IV) oxide (MnO2) catalyse?
decomposition of hydrogen peroxide
2 H2O2 —> 2 H2 + O2
What are catalysis by transition metals important for?
industrial processes
Why are catalysts important in industrial processes?
- they reduce energy usage so reactions can take place at lower temps
- allow alternative reactions to be used which would be to slow to take place under reasonable conditions
- may have better percentage yield or atom economy
Why do transition metals form coloured compounds?
they have a patially filled d subshell
What is a complex ion?
a central transition metal ion is surrounded by ligands bonded by dative covalent bonds
What is a ligand?
an ion or molecule with a lone pair of electrons which it donates to a central metal ion by forming a dative covalent bond with it
What is a hexaaqua ion?
a complex ion containing 6 water molecules
