The d-and f-Block Elements

Introduction to Transition Elements

Position in the Periodic Table

• Their position is in between s- and p- block elements.

• There are four rows of transition elements − 3d, 4d, 5d, and 6d. The fourth row of 6d is still incomplete.

Electronic Configuration

• General outer electronic configuration is (n −1)d¹⁻¹⁰ ns¹⁻².

• But this generalization has several exceptions as there is very little difference in energy between (n − 1)d and ns orbitals. For example, Cr has electronic configuration 3d⁵ 4s¹ instead of 3d⁴ 4s². Cu has electronic configuration 3d¹⁰ 4s¹ instead of 3d⁹ 4s².

• Outer electronic configurations of the transition elements in the ground state are listed in the following tables:

1st series			2nd series
Element	Atomic number	Outer electronic configuration	Element	Atomic number	Outer electronic configuration
Sc	21	3d14s2	Y	39	4d15s2
Ti	22	3d24s2	Zr	40	4d25s2
V	23	3d34s2	Nb	41	4d45s1
Cr	24	3d54s1	Mo	42	4d55s1
Mn	25	3d54s2	Tc	43	4d65s1
Fe	26	3d64s2	Ru	44	4d75s1
Co	27	3d74s2	Rh	45	4d85s1
Ni	28	3d84s2	Pd	46	4d105s0
Cu	29	3d104s1	Ag	47	4d105s1
Zn	30	3d104s2	Cd	48	4d105s2

3rd series			4th series
Element	Atomic number	Outer electronic configuration	Element	Atomic number	Outer electronic configuration
La	57	5d16s2	Ac	89	6d17s2
Hf	72	5d26s2	Rf	104	6d27s2
Ta	73	5d36s2	Db	105	6d37s2
W	74	5d46s2	Sg	106	6d47s2
Re	75	5d56s2	Bh	107	6d57s2
Os	76	5d66s2	Hs	108	6d67s2
Ir	77	5d76s2	Mt	109	6d77s2
Pt	78	5d96s1	Ds	110	6d87s2
Au	79	5d106s1	Rg	111	6d107s1
Hg	80	5d106s2	Uub	112	6d107s2

• Zn, Cd, and Hg are not regarded as transition elements.

• Reason − The orbitals of these elements are completely-filled. [Electronic configuration is (n − 1) d¹⁰ ns²]

• Ions of configuration d¹⁻⁹ have similar magnetic and electronic properties.

• Elements with partially-filled d-orbitals exhibit certain characteristic properties such as showing a variety of oxidation states, formation of coloured ions, and formation of complex with a variety of ligands.

• They and their compounds have catalytic property and are paramagnetic in nature.

Position in the Periodic Table

• Their position is in between s- and p- block elements.

• There are four rows of transition elements − 3d, 4d, 5d, and 6d. The fourth row of 6d is still incomplete.

Electronic Configuration

• General outer electronic configuration is (n −1)d¹⁻¹⁰ ns¹⁻².

• But this generalization has several exceptions as there is very little difference in energy between (n − 1)d and ns orbitals. For example, Cr has electronic configuration 3d⁵ 4s¹ instead of 3d⁴ 4s². Cu has electronic configuration 3d¹⁰ 4s¹ instead of 3d⁹ 4s².

• Outer electronic configurations of the transition elements in the ground state are listed in the following tables:

…

1st series			2nd series
Element	Atomic number	Outer electronic configuration	Element	Atomic number	Outer electronic configuration
Sc	21	3d14s2	Y	39	4d15s2
Ti	22	3d24s2	Zr	40	4d25s2
V	23	3d34s2	Nb	41	4d45s1
Cr	24	3d54s1	Mo	42