Transition metal

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Transition metals in the periodic table
Hydrogen (diatomic nonmetal)
Helium (noble gas)
Lithium (alkali metal)
Beryllium (alkaline earth metal)
Boron (metalloid)
Carbon (polyatomic nonmetal)
Nitrogen (diatomic nonmetal)
Oxygen (diatomic nonmetal)
Fluorine (diatomic nonmetal)
Neon (noble gas)
Sodium (alkali metal)
Magnesium (alkaline earth metal)
Aluminium (post-transition metal)
Silicon (metalloid)
Phosphorus (polyatomic nonmetal)
Sulfur (polyatomic nonmetal)
Chlorine (diatomic nonmetal)
Argon (noble gas)
Potassium (alkali metal)
Calcium (alkaline earth metal)
Scandium (transition metal)
Titanium (transition metal)
Vanadium (transition metal)
Chromium (transition metal)
Manganese (transition metal)
Iron (transition metal)
Cobalt (transition metal)
Nickel (transition metal)
Copper (transition metal)
Zinc (transition metal)
Gallium (post-transition metal)
Germanium (metalloid)
Arsenic (metalloid)
Selenium (polyatomic nonmetal)
Bromine (diatomic nonmetal)
Krypton (noble gas)
Rubidium (alkali metal)
Strontium (alkaline earth metal)
Yttrium (transition metal)
Zirconium (transition metal)
Niobium (transition metal)
Molybdenum (transition metal)
Technetium (transition metal)
Ruthenium (transition metal)
Rhodium (transition metal)
Palladium (transition metal)
Silver (transition metal)
Cadmium (transition metal)
Indium (post-transition metal)
Tin (post-transition metal)
Antimony (metalloid)
Tellurium (metalloid)
Iodine (diatomic nonmetal)
Xenon (noble gas)
Caesium (alkali metal)
Barium (alkaline earth metal)
Lanthanum (lanthanide)
Cerium (lanthanide)
Praseodymium (lanthanide)
Neodymium (lanthanide)
Promethium (lanthanide)
Samarium (lanthanide)
Europium (lanthanide)
Gadolinium (lanthanide)
Terbium (lanthanide)
Dysprosium (lanthanide)
Holmium (lanthanide)
Erbium (lanthanide)
Thulium (lanthanide)
Ytterbium (lanthanide)
Lutetium (lanthanide)
Hafnium (transition metal)
Tantalum (transition metal)
Tungsten (transition metal)
Rhenium (transition metal)
Osmium (transition metal)
Iridium (transition metal)
Platinum (transition metal)
Gold (transition metal)
Mercury (transition metal)
Thallium (post-transition metal)
Lead (post-transition metal)
Bismuth (post-transition metal)
Polonium (post-transition metal)
Astatine (metalloid)
Radon (noble gas)
Francium (alkali metal)
Radium (alkaline earth metal)
Actinium (actinide)
Thorium (actinide)
Protactinium (actinide)
Uranium (actinide)
Neptunium (actinide)
Plutonium (actinide)
Americium (actinide)
Curium (actinide)
Berkelium (actinide)
Californium (actinide)
Einsteinium (actinide)
Fermium (actinide)
Mendelevium (actinide)
Nobelium (actinide)
Lawrencium (actinide)
Rutherfordium (transition metal)
Dubnium (transition metal)
Seaborgium (transition metal)
Bohrium (transition metal)
Hassium (transition metal)
Meitnerium (unknown chemical properties)
Darmstadtium (unknown chemical properties)
Roentgenium (unknown chemical properties)
Copernicium (transition metal)
Ununtrium (unknown chemical properties)
Flerovium (post-transition metal)
Ununpentium (unknown chemical properties)
Livermorium (unknown chemical properties)
Ununseptium (unknown chemical properties)
Ununoctium (unknown chemical properties)

In chemistry, the term transition metal (or transition element) has two possible meanings:


Jensen[4] reviews the history of the terms "transition element" (or "metal") and "d-block". The word transition was first used to describe the elements now known as the d-block by the English chemist Charles Bury in 1921, who referred to a transition series of elements during the change of an inner layer of electrons (for example n=3 in the 4th row of the periodic table) from a stable group of 8 to one of 18, or from 18 to 32.[5]



Transition metals in the d-block
Group 3 4 5 6 7 8 9 10 11 12
Period 4 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30
Period 5 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48
Period 6 57–71 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80
Period 7 89–103 Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 Ds 110 Rg 111 Cn 112

The typical electronic structure of transition metal atoms can be written as [ ]ns2(n-1)dm, following the Madelung rule where the inner d orbital is predicted to be filled after the valence-shell s orbital. This is actually not the case; the 4s electrons are higher in energy than the 3d as shown spectroscopically. An ion such as Fe2+
has no 4s electrons: it has the electronic configuration [Ar]3d6 as compared with the configuration of the atom, [Ar]4s23d6.

The elements of groups 3–12 are now generally recognized as transition metals, although the elements La-Lu and Ac-Lr and Group 12 attract different definitions from different authors.

  1. Many chemistry textbooks and printed periodic tables classify La and Ac as Group 3 elements and transition metals, since their atomic ground-state configurations are s2d1 like Sc and Y. The elements Ce-Lu are considered as the “lanthanide” series (or “lanthanoid” according to IUPAC) and Th-Lr as the “actinide” series.[6][7] The two series together are classified as f-block elements, or (in older sources) as “inner transition elements”.
  2. Some inorganic chemistry textbooks include La with the lanthanides and Ac with the actinides.[8][9][10] This classification is based on similarities in chemical behaviour, and defines 15 elements in each of the two series even though they correspond to the filling of an f subshell which can only contain 14 electrons.
  3. A third classification defines the f-block elements as La-Yb and Ac-No, while placing Lu and Lr in Group 3.[4] This is based on the aufbau principle (or Madelung rule) for filling electron subshells, in which 4f is filled before 5d (and 5f before 6d), so that the f subshell is actually full at Yb (and No) while Lu (and Lr) has an [ ]s2f14d1 configuration. However La and Ac are exceptions to the Aufbau principle with electron configuration [ ]s2d1 (not [ ]s2f1 as the aufbau principle predicts) so it is not clear from atomic electron configurations whether La or Lu (Ac or Lr) should be considered as transition metals. Eric Scerri has proposed placing Lu and Lr in group 3 on the grounds of continuous sequences of atomic numbers in an expanded or long-form periodic table.[11]

Zinc, cadmium, and mercury are sometimes excluded from the transition metals[4] as they have the electronic configuration [ ]d10s2, with no incomplete d shell.[12] In the oxidation state +2 the ions have the electronic configuration [ ] d10. However, these elements can exist in other oxidation states, including the +1 oxidation state, as in the diatomic ion Hg2+
. The group 12 elements Zn, Cd and Hg may be classed as post-transition metals in this case, because of the formation of a covalent bond between the two atoms of the dimer. However, it is often convenient to include these elements in a discussion of the transition elements. For example, when discussing the crystal field stabilization energy of first-row transition elements, it is convenient to also include the elements calcium and zinc, as both Ca2+
and Zn2+

The recent synthesis of mercury(IV) fluoride (HgF
) has been taken by some to reinforce the view that the group 12 elements should be considered transition metal,[13] but some authors still consider this compound to be exceptional.[14]

Position in the Periodic Table[edit]

The d-block as stated earlier, is present in the centre of the long form of periodic table. These are flanked or surrounded by elements belonging to s and p-blocks on both sides. These are called transition elements since they represent a transition i.e., there is a change from metallic character of s-block elements to non-metallic character of p-block elements through d-block elements which are also metals. As pointed above there are four transition series in this block. Since the filling of electrons takes place in (n-1)d orbitals, the periods to which these series belong, is actually one more than the actual series. For example, the elements included in 3d series belong to fourth period ; the elements included in 4d series belong to the fifth period and so on.

Electronic configuration[edit]

The general electronic configuration of the d-block elements is [Inert gas] (n-1)d1-10n s1-2 The d-sub-shell is the penultimate (last but one) sub-shell and is denoted as (n-1) d-sub-shell. The number of s electrons may vary from one to two. The s-sub-shell in the valence shell is represented as the ns sub-shell. However, palladium (Pd) is an exception with no electron in the s-sub shell. In the periodic table, the transition metals are present in ten groups (3 to 12). Group-2 belongs to the s- block with an ns2 configuration.

The elements in group-3 have an ns2(n-1)d1 configuration. The first transition series is present in the 4thperiod, and starts after Ca (Z=20) of group-2 which has configuration [Ar]4s2. The electronic configuration of scandium (Sc), the first element of group-3 with atomic number Z=21 is[Ar]4s23d1. As we move from left to right, electrons are added to the same d-sub-shell till it is complete. The element of group-12 in the first transition series is zinc (Zn) with configuration [Ar]4s23d10. Since the electrons added fill the (n-1)d orbitals, the properties of the d-block elements are quite different from those of s and p block elements in which the filling occurs either in s or in p-orbitals of the valence shell. The electronic configuration of the individual elements present in all the transition series are given below:

First (3d) Transition Series (Sc-Zn)

Element Sc Ti V Cr Mn Fe Co Ni Cu Zn
Config. 3d14s2 3d24s2 3d34s2 3d54s1 3d54s2 3d64s2 3d74s2 3d84s2 3d104s1 3d104s2

Second (4d) Transition Series (Y-Cd)

Element Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
Config. 4d15s2 4d25s2 4d45s1 4d55s1 4d55s2 4d75s1 4d85s1 4d105s0 4d105s1 4d105s2

Third (5d) Transition Series (Lu-Hg)[15]

At.No 71 72 73 74 75 76 77 78 79 80
Element Lu Hf Ta W Re Os Ir Pt Au Hg
Config. 5d16s2 5d26s2 5d36s2 5d46s2 5d56s2 5d66s2 5d76s2 5d96s1 5d106s1 5d106s2

Fourth (6d) Transition Series (Lr-Cn)

At. No. 103 104 105 106 107 108 109 110 111 112
Element Lr Rf Db Sg Bh Hs Mt Ds Rg Cn
Config. 7s27p1 6d27s2 6d37s2 6d47s2 6d57s2 6d67s2 6d77s2 6d87s2 6d97s2 6d107s2

A careful look at the electronic configuration of the elements reveals that there are certain exceptions shown by Pt, Au and Hg.. These are either because of the symmetry or nuclear-electron and electron-electron force.

The (n-1)d orbitals that are involved in the transition metals are very significant because they influence such properties as magnetic character, variable oxidation states, formation of colored compounds etc. The valence s(ns) and p(np) orbitals have very little contribution in this regard since they hardly change in the moving from left to the right in a transition series. In transition metals, there is a greater horizontal similarities in the properties of the elements in a period in comparison to the periods in which the d-orbitals are not involved. This is because in a transition series, the valence shell electronic configuration of the elements do not change. However, there are some group similarities as well.

Characteristic properties[edit]


  • the formation of compounds in many oxidation states, due to the relatively low reactivity of unpaired d electrons.[16]

Coloured compounds[edit]

From left to right, aqueous solutions of: Co(NO
(red); K
(orange); K
(yellow); NiCl
(turquoise); CuSO
(blue); KMnO






Oxidation states[edit]

, and +5, such as VO3−

, which contain a Ga-Ga bond formed from the unpaired electron on each Ga atom.[18] Thus the main difference in oxidation states, between transition elements and other elements is that oxidation states are known in which there is a single atom of the element and one or more unpaired electrons.

The maximum oxidation state in the first row transition metals is equal to the number of valence electrons from titanium (+4) up to manganese (+7), but decreases in the later elements. In the second and third rows the maximum occurs with ruthenium and osmium (+8). In compounds such as [MnO
and OsO
the elements achieve a stable octet by forming four covalent bonds.

(oxidation state zero) and [Fe(CO)



Main article: magnetochemistry

Transition metal compounds are paramagnetic when they have one or more unpaired d electrons.[19] In octahedral complexes with between four and seven d electrons both high spin and low spin states are possible. Tetrahedral transition metal complexes such as [FeCl


Catalytic properties[edit]


Other properties[edit]

As implied by the name, all transition metals are metals and conductors of electricity.


Many transition metals can be bound to a variety of ligands.[20]

See also[edit]


  2. ^ R.H. Petrucci, W.S. Harwood and F.G. Herring “General Chemistry” (8th ed, Prentice-Hall 2002), p.341-2
  3. ^ C.E. Housecroft and A.G. Sharpe “Inorganic Chemistry” (2nd ed, Pearson Prentice-Hall 2005), p.20-21
  4. ^ a b c Jensen, William B. (2003). "The Place of Zinc, Cadmium, and Mercury in the Periodic Table". Journal of Chemical Education 80 (8): 952–961. Bibcode:2003JChEd..80..952J. doi:10.1021/ed080p952. 
  6. ^ Petrucci, R. H. et al. (2002), “General Chemistry”, 8th edn, Prentice-Hall, pp. 49–50, 951
  7. ^ Miessler, G. L. and Tarr, D. A. (1999) “Inorganic Chemistry”, 2nd edn, Prentice-Hall, p. 16
  9. ^ Cotton, F.A. and Wilkinson, G. (1988) “Inorganic Chemistry”, 5th edn, Wiley , pp. 626–7
  10. ^ Housecroft, C. E. and Sharpe, A. G. (2005) “Inorganic Chemistry”, 2nd edn, Pearson Prentice-Hall, p. 741
  11. ^ Scerri,E.R. (2011), "A Very Short Introduction to the Periodic Table, Oxford University Press.
  13. ^ Wang, Xuefang; Andrews, Lester; Riedel, Sebastian; Kaupp, Martin (2007). "Mercury Is a Transition Metal: The First Experimental Evidence for HgF4". Angew. Chem. Int. Ed. 46 (44): 8371–8375. doi:10.1002/anie.200703710. PMID 17899620. 
  15. ^ This table follows the proposal of Scerri (see above) and considers Lu rather than La to be a transition metal in the 5d series. As noted in the section on Classification, not all chemists agree.
  16. ^ Matsumoto, Paul S (2005). "Trends in Ionization Energy of Transition-Metal Elements". Journal of Chemical Education 82 (11): 1660. Bibcode:2005JChEd..82.1660M. doi:10.1021/ed082p1660. 
  18. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.  p. 240