periodicity– transition metals Flashcards
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
why does m.p. decrease from Fe to Zn?
- less unpaired e- in 3d subshell
- weaker metallic bonding
why are d-block elements more dense than s-block
- stronger metallic bond strength
- smaller atomic radii
thus more closely packed
why does Mn have a lower m.p.?
Cr: 4s1 3d5
Mn: 4s2 3d5
- Mr has less unpaired e-
- thus weaker metallic bonds
- lower m.p.
the density of d-block elements ______ across the period as…
incr
- atomic radii decr slightly
- more atoms can be packed closely together
what are the two forms of magnetism?
paramagnetism, diamagnetism
paramagnetism is when..
an ion, molecule, atom has unpaired e-
paramagnetic substances are [attracted/repelled] by a magnetic field, as…
attracted
- unpaired e- give rise to a magnetic field that can be affected by external magnetic field
diamagnetism is caused by ______ e-.
paired
how do diamagnetic substances respond to a magnetic field?
they are repelled
how do you find the maximum oxidation state of a TM?
no. 4s e- + no. 4d e-
what is a catalyst?
a substance that incr the ROR by providing an alternative rxn pathway that lowers Ea
what are the two types of catalysts?
- homogenous
- heterogenous
heterogenous catalysts are in a ______ ________ as the reactants
diff phase
how do TMs act as heterogenous catalysts? (3)
- reactants adsorb to e active sites of catalyst
- weakens the covalent bonds within the rxt molecules
- lowers Ea for the rxn
- it incr surface conc and ensures proper orientation for the rxn
- products deabsorb fr e active site -> freeing up active sites
why can TMs act as homogenous catalysts? (1)
- they can form variable oxidation states
- i.e. they can be easily converted fr one ox state to another
what are ligands? (defin.)
an anion or molecule that has at least one lone pair of e- that can be donated into the vacant orbitals in the central metal atom
what are complexes? (defin.)
a complex consists of a central metal atom or ion surrounded by other ions or molecules called ligands through dative bonds
ligands act as _______
Lewis bases
why can TMs form complexes? (2)
their metal cations have
1. high charge densities
- hence high polarising power -> cations can attract lone pair of e- from ligands
2. vacant, low-lying 3d orbitals
- can accept lone pair of e- donated by ligands -> dative bond formed
ligands can be _________ charged or ___________ charged
neutrally or negatively
why are ligands Lewis bases?
they are e- pair donors
a ligand that forms 2 dative bonds is called…
bidentate
what is ligand exchange?
a stronger ligand replacing a weaker ligand from a cation complex
ligand exchange can be seen through observing a _______________
colour change
why are TM complexes coloured? (short)
due to the presence of partially filled d-orbitals
why are some TM complexes colourless?
- complexes with Sc3+ ion -> 3d subshell is empty
- Zn2+ -> 3d subshell is full
why do transition metals form coloured compounds? (4)
- in the presence of ligands, the d orbital splits into 2 energy levels
- an e- in the lower energy level is able to be promoted to the higher energy level
- by absorbing a wavelength of light in the visible region
- the complimentary colour of the light absorbed is observed
what affects the colour of complexes? (2)
- nature and oxidation state of TM
- nature of ligands
how does the nature and oxidation state of TM affect the colour of complexes?
- diff no. of e- in the d orbitals repel e- of ligands to a diff extent
- gives rise to diff energy gaps -> diff colour
the nature of ligands affects the colours of complexes as…
diff ligands split the d-orbitals to a diff extent
the longest wavelength is…
red
what is the shortest wavelength?
violet
