All d block elements excluding
scandium (ion = [Ar] 3d^0) and
zinc (ion = [Ar] 3d^10)
4s orbitals are filled up first as they are lower in energy. However,
once 3d orbitals are occupied, shielding effect occurs (3d electrons
shield 4s electrons), effective nuclear charge of 4s orbitals
increases. During ion formation, 4s electrons are removed first.
exception to general pattern of
electronic configuration: Cr ( [Ar] 3d^5
4s^1) and Cu ( [Ar] 3d^10 4s^1)
ELECTRONIC
CONFIGURATION
PHYSICAL PROPERTIES
(across the period)
Atomic radii trend
decreases slightly
Annotations:
-Across the period:
* nuclear charge increases
* shielding effect increases (unlike s block elements which remain constant) due to filling in of d orbitals (unlike s block metals which fills in outermost orbital)
-effective nuclear charge increases slightly
-atomic radii decreases slightly
Ionic radii trend
decreases slightly for M^3+
Annotations:
no explanation for this, no trend for M^2+
Boiling and melting
points
higher than s block
elements
Annotations:
-able to use both 3d and 4s electrons for metallic bonding due to close proximity in their energies (s block elements can only use their valence electrons i.e. 1-2 electrons)
-more energy needed to break the stronger metallic bond
First I.E trend
increases slightly
Annotations:
-slight increase in effective nuclear charge only
-therefore slight increase in energy needed to remove a 4s electron
Density
generally very high
Annotations:
-higher atomic mass and small atomic radius
-across the period, atomic radii (vol.) decreases and atomic mass (mass) increases
-density increases
Electrical
conductivity
Cu: very good
conductor of heat and
electricity
Annotations:
-due to ability to use both 3d and 4s electrons due to their close proximity in energies
-unlike block s elements that are unable to use inner shell electrons due to very diff energies from the valence electrons