periodicity– transition metals
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what are transition metals? (short defin.)
• a d-block element that forms 1 or more stable ions w partially filled d subshell
what are the exceptions in the transition metals?
Zn, Sc3+, Cu+
why is Zn not considered a transition metal?
• it forms only 1 ion, Zn2+ • Zn2+ has a fully filled d subshell
why is Sc3+ not considered a transition metal?
it has no e- in its d subshell
why is Cu+ not a transition metal?
it has a fully filed d subshell
____ orbitals are filled before ___
4s, 3d
in transition metals, 4s is filled before 3d except for…
Cr and Cu
why do Cr and Cu not have a fully filled 4s orbital?
• Cr -> 3d orbitals are half filled and more stable than fully filled 4s • Cu -> 3d orbitals are fully filled and stable
d-block metals have a [higher/lower] m.p. compared to s-block metals
higher
is the atomic radii of transition metals generally larger or smaller than s-block metals?
smaller
transition metals are [more/less] dense than s-block metals
more
_____ metals are poorer conductors of electricity compared to ______ metals
s-block, d-block
why is the atomic and ionic radii of d-block elements smaller than s-block elements?
• d subshell SE not as effective as p subshell • as d subshells are more diffused • valence shell for d-block elements exp greater nuclear attraction -> smaller radii
how does the atomic radius change across the period and why?
• decr slightly: • due to nuclear charge incr slightly -> SE incr slightly -> ENC increases slightly • thus radius decr slightly
what is the trend for ionisation energies across the period?
• incr slightly
why does ionisation energies incr slightly from s-block to d-block
• p subshell provides better shielding than d subshell • d subshells more diffused • valence shell of d-block elements exp greater nuclear attraction • thus greater IE for d-block
there is a ______ incr from 1st to 2nd IE, and a _______ incr from 2nd to 3rd IE
small, large
there is a small incr from 1st to 2nd IE because…
both first and second electrons are removed from the same orbital, 4s
the large increase from 2nd to 3rd IE in d block elements is because…
• third electron is removed from 3d subshells • SE decr -> ENC incr
why is the 2nd IE of Mn lower than that of Cr?
• 2nd e- removed from Mn is 4s • 2nd e- removed from Cr is 3d • 4s is in outer shell -> experiences weaker ENC
why is the 3rd IE of Mn>Fe?
• Fe = 3d6 • electron removed is in the same orbital as another electron • inter-electronic repulsion • thus less energy req
why do trans elements have greater m.p. than s-block?
• 3d + 4s energies are relatively similar • TM can lose more valence e- • thus more delocalised e- • stronger electrostatic FOA btw metal cation and sea of delocalised e- • TMS have stronger metallic bonding -> higher m.p.
what is the trend of m.p. across the d-block?
incr then decr
why does m.p. increase from Sc to Cr?
• Cr has 5 unpaired e- (3d) • Sc has 1 unpaired e- (3d) • Cr has more unpaired e- in 3d subshell • thus stronger metallic bonding