d and f block elements Flashcards
Transition elements
These are elements that have incompletely filled d orbitals either in their neutral state or in any of their oxidation states
What constitutes the d block elements?
The elements of group 3 to 12, across 4 periods( except Zn, Cd and Hg)
3d elements
Sc Ti V Cr Mn Fe Co Ni Cu Zn
4d elements
Y Zr Nb Mo Tc Ru Rd Pd Ag Cd
5d elements
La Hf Ta W Re Os Ir Pt Au Hg
6 d elements
Ac Rf Db Sg Bh Hs Mt Ds Rg Cn
General configuration
ns1-2 (n-1)d 1-10
Why do d block elements have so many exceptional electronic configurations?
Due to small energy difference between ns and n-1 d subshells
Configuration of Pd
5s0 4d10
Why are d orbitals influenced by the surrounding atoms
They protrude out of the atom more than other orbitals like s and p.
Physical properties of d block elements
Typical metallic properties
1. High tensile strength
2. Ductility
3. Malleability
4. Thermal and electrical conductivity
5. Metallic lustre
6. High MP and BP
7. Low volatility
With the exceptions of Zn, Cd and Hg and Mn they typically show one or more metallic characters at a given temperature.
Lattice structures
Group 3 and 4- HCP
5 and 6- BCC
7 and 8- HCP except Mn
9,10,11- CCP
12- a typical metallic structure
Nature of bonding in transition metals
They show metallic bonding
This is due to the delocalization of s and d electrons.
Metallic bonding is stronger in the case of middle members due to greater no. of unpaired electrons.
Strength of metallic bonding also increases as we go down a group due to increase in size and greater delocalization
Why do transition elements have hardness and high melting and boiling points?
High no. of unpaired electrons in ns and (n-1 )d subshells. The energy difference between these subshells is also low. Thus due t the delocalization of these unpaired electrons they show metallic bonding and thus metallic characters.
Variation in melting points among transition elements
Among 3d series, melting point increases till V and begins decreasing till Mn. Mn has low melting point due to its stable configuration( thus, no delocalization). It increases till Fe and drops till Zn( lowest melting point in 3d series)
- Highest in 3d series- Vanadium
- Similar trend is observed for 4d series
- In 5 d series it increases till Tungsten and keeps dropping till Mercury
Lowest melting point
Mercury (-38C)
Highest melting point in transition elements
Tungsten (2800 C)
Variation of enthalpy of atomization among transition elements
Usually high except for group 12 elements.
Among 3d series, V has the highest atomization enthalpy which is 515kJ/mol
Lowest among 3d series is Zn
As we go down the group enthalpy of atomization increases as metallic bonding increases
What kind of metals are noble in reactions
Those with high atomization enthalpy
Among transition elements which has the lowest enthalpy of atomization
Copper
Metallic bonding is proportional to
No. of valence electrons
Variations in atomic and ionic sizes in transition elements
Generally decreases across a series but increases down the group.
Sc- 164pm
T- 147 pm
V- 135pm
Cr- 129pm
Mn-137 pnm due to repulsions between electrons of d5 configuration
Fe- 125 pm
Co-125 pm
Ni- 126pm
Cu-128 pm
Zn- 137 pm due to d10 configuration
Largest among 3d series- Sc
- Increases from 3d to 4d but there is only a marginal increase in the case of 5d. This is because 4f electrons have to be filled before 5d orbitals and this results in a decrease of atomic radius known as lanthanoid contraction
Lanthanoid contraction
Lanthanide contraction is the gradual decrease in the size of lanthanide atoms and ions as the atomic number increases. This is why 4d and 5d have similar radii. In the case of lanthanides, the electrons have to get added to 4f subshell before 5d, which has poor shielding effect. This results in a considerable decrease in size among the atoms from Ce to Lu as f electrons don’t repel each other or electrons from other subshells.
- Note: This also results in similar physical and chemical properties
Exception in Lanthanide contraction
Slight increase in the size of Eu
Size of Zr and Hf
Almost same . Approximately 160 pm
What is more intense - lanthanide or actinoid contraction?
Actinoid contraction
In the case of isoelectronic species
Greater the charge, lower the size
Variation of density
Due to small volume and high mass, density is usually high( >5g/cm3) Except for Sc, Ti and Y
- Among 3d series, Sc has the lowest density (3.1g/cm3) and Cu has the highest(8.9 g/cm3)
- In the entire d block, Os, followed by Iridium, has the highest density and Sc has the lowest
