5.3.1 Transition Elements Flashcards
what are d-block elements
- located between group 2 and 13
- where the 3d subshell has the highest energy, and electrons are added to this orbital
explain characteristics of d-block elements, since they are metallic
- high melting/boiling point
- shiny in appearance
- conduct electricity/heat
what is electron configuration
shows the arrangement of electrons in shells and sub-shells
- electrons occupy orbitals in order of increasing energy
what is the electron configuration of Zn
1s2 2s2 2p6 3s2 3p6 4s2 3d10 (could also just write 3d10 and then 4s2)
what’s important to remember when transition metals form ions
- they lose their 4s electrons before 3d
- (when making the atoms, reverse, so 4s fills before 3d)
what’s special about the electron configurations of chromium and copper
- they are 4s1 3d5 and 4s1 3d10
- as having a half filled/fully filled 3d subshell gives them extra stability
what are transition elements
d-block elements that form at least 1 ion with a partially filled d-subshell
give examples of 2 d-block elements that are not transition metals
zinc and scandium
why is zinc and scandium not transition metals
- Zinc only forms Zn2+ ions, so lose both 4s electrons, leaving behind 3d10 (FULLY FILLED D ORBITAL)
- Scandium only forms Sc3+ ions, so loses its 4s electrons, as well as its only 3d1 electron (FULLY EMPTY D ORBITAL)
what are the 3 properties of transition metals
1) form compounds in which the transition element has different oxidation state
2) form coloured compounds
3) the elements and their compounds can act as catalysts
explain transition metals having variable oxidation states
- e.g. iron (II) chloride and iron (III) chloride
- all transition metals form 2+ ions
- the number of oxidation states a transition metal has increases across the series to manganese (+5 to +7), then decreases to +3
- each oxidation state has a distinct colour
- species with transition metals in their highest oxidation states are really strong oxidising agents
explain transition metals forming coloured compounds
- the colour of a solution is linked to the partially filled d-orbital of the ion, and varies with different oxidation states
- e.g. Fe(II) - pale yellow - 3p6 3d6
- Fe(III) - yellow - 3p6 3d5
- e.g. Cr (III) - green
- Cr (VI) - yellow/orange
what is a catalyst
increases the rate of chemical reaction via providing an alternative reaction pathway, but remains unchanged itself
explain transition metals as catalysts
- can be HETEROGENEOUS catalysts , where in a different state to the reactants
- e.g. in Haber process: N2 + 3H ⇌ 2NH3 - uses IRON CATALYST
- e.g. catalytic decomposition of hydrogen peroxide: 2H2O2 → 2H2O + O2 - uses MnO2 CATALYST
- e.g. contact process of producing sulfur trioxide via oxidation: 2SO2 + O2 ⇌ 2SO3 - uses VANADIUM OXIDE ION
- e.g. hydrogenation of vegetable fats in making margarine - uses NICKEL CATALYST
- can be HOMOZYGOUS catalysts, where they are in the same state as the reactants
- e.g. reaction of zinc with acids: Zn + H2SO4 → ZnSO4 + H2 - needs Cu2+ CATALYST
- e.g. S2O8 2- + I- → 2SO4 2- + I2 - uses Fe2+ catalyst, which reacts in the first step of the reaction to Fe3+, and then is regenerated in the second step
what type of special ions can d-block elements form
- complex ions, though not restricted to d-block
how are complex ions formed
when one or more molecules or negatively charged ions bond to a central metal ion
what are ligands
a molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond (dative covalent bond)
what is a coordinate bond
a special kind of covalent bond formed when one of the bonded atoms provides both of the electrons in a shared pair
what is coordination number
the number of coordinate bonds attached to the central metal ion
how should you show complex ions in a formula
- complex ion is enclosed inside square brackets
- the overall charge is shown outside the bracket
- the ligand is found inside round brackets, with the number outside
- e.g. [Cr(H2O)6]3+ ( where Cr3+ is the central metal ion, and each H2O molecule donates a lone pair of electrons from the O atom to Cr3+)
what would the overall charge of a complex ion be
the sum of the charges of the central metal ion and any ligand present
what are the two charges a ligand can have
neutral or negative
what is a monodentate ligand
a ligand that is able to donate one pair of electrons to a central metal ion
what are examples of monodentate ligands
- H2O:
- :NH3
- :Cl-
- :CN-
- :OH-