d and f blocks Flashcards
what are d block elements
The d-block elements are those elements in which the last electron enters the d–subshell
of penultimate shell. The general electronic configuration of these elements is (n – 1) d(1–10)
ns (1–2), where n
is outermost shell.
what is a transition element?
A transition element is defined as an element which
has unpaired electrons in its d subshell
Zn, Cd, Hg are not transition elements why?
Zn, Cd, Hg etc. [(n – 1)d10] are d-block
elements, but not transition metals because these have completely filled d-orbitals.
Alloy formation how?
: The transition metals have similar radii and other characteristics. Therefore, these
metals can mutually substitute their position in their crystal lattices and form alloys. The alloys so
formed are hard and often have high melting point. Various types of steel, brass, bronze are examples
of this type of alloy.
Interstitial compounds how?
Interstitial compounds are those in which small atoms occupy the interstitial
sites in the crystal lattice. Interstitial compounds are well known for transition metals because small-
sized atoms of H, B, C, N, etc., can easily occupy positions in the voids present in the crystal lattices
of transition metals.
Most of the transition metal ions in solution as well as in solid states are coloured. why?
This is due
to the partial absorption of visible light. The absorbed light promotes the electron from one orbital to
another orbital of the same d-subshell. Since the electronic transition occurs within the d-orbitals of
the transition metal ions, they are called d–d transitions. It is because of these d–d transitions occurring
in a transition metal ion by absorption of visible light that they appear coloured.
Complex formation why?
The tendency to form complex ions is due to
(i) the high charge on the transition metal ions,
(ii) the availability of d-orbitals for accommodating electrons donated by the ligand atoms.
transition elements are dash in nature
paramagnetic
variable oxidation states why ?
durto participation of n-1 d (higher)orbitals and ns (lower)orbitals
high Melting and boiling points why?
This is due to participation of ns and nsd-1 orbitals
why is there increase in ionisation enthalpy?
The increase in ionisation enthalpy is due to increase in nuclear charge with increase in atomic number which tends to attract the electron cloud with greater force.
why do they multiple oxidation states?
this is due to its participation of ns and n-1 d orbitals.
lanthanoid contraction
filling of 4f orbitals before 5f orbitals.there is a regular decrese in atmoic radii with increase in atomic number.
lanthanoid contraction cause
2nd and 3rd d series exhibit very similar raddi and have very similar chemical and physical properties. eg zr and hf
lanthanoid contraction consequence
