CBSE Class 12 Chemistry Notes And Questions For The D And F Block Elements Part C
DOWNLOADED FROM WWW.STUDIESTODAY.COM
DOWNLOADED FROM WWW.STUDIESTODAY.COM
d – AND f – BLOCK ELEMENTS
Electronic Configuration of Transition Metal/Ions
The d-block element is called transition metal if it has partly filled d-orbitals in the ground state as well as in its oxidised state.
The general electronic configuration of transition metal is (n–1) d1–10ns1–2.
Exceptions in electronic configuration are due to (a) very little engery difference between (n–1) d and ns orbitals and (b) extra stability of half filled and completely filled orbitals in case of Cr and Cu in 3d series.
Cr : Is 2 2s2 2p6, 3s2 3p6 4s1 3d5
Cu : Is2 2s2 2p6, 3s2 3p6 4s1 3d10
To write the electronic configuration of Mn+, the electrons are first removed from ns orbital and then from (n - 1) d orbitals of neutral, atom (if required).
For example, the electronic configuration of Cu+, Cu2+ and Cr3+ are respectively
3d10 4s°, 3d9 4s° and 3d3 4s°.
m o .c
y a d with the help of above.
The following questions can be answered o t
(i)
Scandium (Z = 21) is a transition s element but zinc (Z = 30) is not. e i
(ii)
Copper (Z = 29) and silver
(Z = 47) both have fully filled d-orbitals dthese u
i.e., (n - 1) d . why are elements are regarded as transition t s elements? . w (iii)
Which of the d-block elements are not regarded as transition w elements? w 10
UNDERSTANDING fus H vap H AND a H
In transition metals unpaired (n - l)d electrons as well as ns electrons take part in interatomic bonding. Larger the number of unpaired (n - 1) d electrons, the stronger is the interatomic bonding and large amount of energy is required to overcome the interatomic interaction.
∆ fus Hθ
M(s)
→ M(1) θ ∆ vap H
M(1)
→ M(vapour)
∆a Hθ
M(s)
→ M(g)
These enthalpies are related as
fus H < Dvap H < a H
DOWNLOADED FROM WWW.STUDIESTODAY.COM
DOWNLOADED FROM WWW.STUDIESTODAY.COM
76
XII – Chemistry
AK
DOWNLOADED FROM WWW.STUDIESTODAY.COM
DOWNLOADED FROM WWW.STUDIESTODAY.COM
The following
DOWNLOADED FROM WWW.STUDIESTODAY.COM
d – AND f – BLOCK ELEMENTS
Electronic Configuration of Transition Metal/Ions
The d-block element is called transition metal if it has partly filled d-orbitals in the ground state as well as in its oxidised state.
The general electronic configuration of transition metal is (n–1) d1–10ns1–2.
Exceptions in electronic configuration are due to (a) very little engery difference between (n–1) d and ns orbitals and (b) extra stability of half filled and completely filled orbitals in case of Cr and Cu in 3d series.
Cr : Is 2 2s2 2p6, 3s2 3p6 4s1 3d5
Cu : Is2 2s2 2p6, 3s2 3p6 4s1 3d10
To write the electronic configuration of Mn+, the electrons are first removed from ns orbital and then from (n - 1) d orbitals of neutral, atom (if required).
For example, the electronic configuration of Cu+, Cu2+ and Cr3+ are respectively
3d10 4s°, 3d9 4s° and 3d3 4s°.
m o .c
y a d with the help of above.
The following questions can be answered o t
(i)
Scandium (Z = 21) is a transition s element but zinc (Z = 30) is not. e i
(ii)
Copper (Z = 29) and silver
(Z = 47) both have fully filled d-orbitals dthese u
i.e., (n - 1) d . why are elements are regarded as transition t s elements? . w (iii)
Which of the d-block elements are not regarded as transition w elements? w 10
UNDERSTANDING fus H vap H AND a H
In transition metals unpaired (n - l)d electrons as well as ns electrons take part in interatomic bonding. Larger the number of unpaired (n - 1) d electrons, the stronger is the interatomic bonding and large amount of energy is required to overcome the interatomic interaction.
∆ fus Hθ
M(s)
→ M(1) θ ∆ vap H
M(1)
→ M(vapour)
∆a Hθ
M(s)
→ M(g)
These enthalpies are related as
fus H < Dvap H < a H
DOWNLOADED FROM WWW.STUDIESTODAY.COM
DOWNLOADED FROM WWW.STUDIESTODAY.COM
76
XII – Chemistry
AK
DOWNLOADED FROM WWW.STUDIESTODAY.COM
DOWNLOADED FROM WWW.STUDIESTODAY.COM
The following