KNOCKHARDY PUBLISHING AN INTRODUCTION TO TRANSITION METAL CHEMISTRY KNOCKHARDY PUBLISHING

DEFINITION OF TRANSITION ELEMENTS Definition D-block elements forming one or more stable ions with partially filled (incomplete) d-sub shells. Properties arise from an incomplete d sub-shell in atoms or ions

THE FIRST ROW TRANSITION ELEMENTS Metallicproperties All the transition elements are metals Strong metallic bonds due to small ionic size and close packing Higher melting, boiling points and densities than s-block metals K Ca Sc Ti V Cr Mn Fe Co m.p. (°C) 63 850 1400 1677 1917 1903 1244 1539 1495 density (g cm-3 ) 0.86 1.55 3 4.5 6.1 7.2 7.4 7.9 8.9

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS POTASSIUM 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s1 ‘Aufbau’ Principle In numerical terms one would expect the 3d orbitals to be filled next. However, because the principal energy levels get closer together as you go further from the nucleus coupled with the splitting into sub energy levels, the 4s orbital is of a LOWER ENERGY than the 3d orbitals so gets filled first.

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS CALCIUM 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 As expected, the next electron in pairs up to complete a filled 4s orbital. This explanation, using sub levels fits in with the position of potassium and calcium in the Periodic Table. All elements with an -s1 electronic configuration are in Group I and all with an -s2 configuration are in Group II.

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS SCANDIUM 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d1 With the lower energy 4s orbital filled, the next electrons can now fill p the 3d orbitals. There are five d orbitals. They are filled according to Hund’s Rule. BUT WATCH OUT FOR TWO SPECIAL CASES.

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS TITANIUM 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d2 The 3d orbitals are filled according to Hund’s rule so the next electron doesn’t pair up but goes into an empty orbital in the same sub level. HUND’S RULE OF MAXIMUM MULTIPLICITY

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS VANADIUM 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d3 The 3d orbitals are filled according to Hund’s rule so the next electron doesn’t pair up but goes into an empty orbital in the same sub level. HUND’S RULE OF MAXIMUM MULTIPLICITY

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS CHROMIUM 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s1 3d5 One would expect the configuration of chromium atoms to end in 4s2 3d4. To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d to give six unpaired electrons with lower repulsion.

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS MANGANESE 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d5 The new electron goes into the 4s to restore its filled state.

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS IRON 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d6 d orbitals are filled according to Hund’s Rule. Electrons continue to pair up. HUND’S RULE OF MAXIMUM MULTIPLICITY

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS COBALT 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d7 Orbitals are filled according to Hund’s Rule. They continue to pair up. HUND’S RULE OF MAXIMUM MULTIPLICITY

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS NICKEL 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d8 Orbitals are filled according to Hund’s Rule. They continue to pair up. HUND’S RULE OF MAXIMUM MULTIPLICITY

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS COPPER 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s1 3d10 One would expect the configuration of copper atoms to end in 4s2 3d9. To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d. HUND’S RULE OF MAXIMUM MULTIPLICITY

ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS ZINC 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s2 3d10 The electron goes into the 4s to restore its filled state and complete the 3d and 4s orbital filling.

ELECTRONIC CONFIGURATIONS K 1s2 2s2 2p6 3s2 3p6 4s1 Ca 1s2 2s2 2p6 3s2 3p6 4s2 Sc 1s2 2s2 2p6 3s2 3p6 4s2 3d1 Ti 1s2 2s2 2p6 3s2 3p6 4s2 3d2 V 1s2 2s2 2p6 3s2 3p6 4s2 3d3 Cr 1s2 2s2 2p6 3s2 3p6 4s1 3d5 Mn 1s2 2s2 2p6 3s2 3p6 4s2 3d5 Fe 1s2 2s2 2p6 3s2 3p6 4s2 3d6 Co 1s2 2s2 2p6 3s2 3p6 4s2 3d7 Ni 1s2 2s2 2p6 3s2 3p6 4s2 3d8 Cu 1s2 2s2 2p6 3s2 3p6 4s1 3d10 Zn 1s2 2s2 2p6 3s2 3p6 4s2 3d10

VARIABLE OXIDATION STATES Arises from the similar energies required for removal of 4s and 3d electrons When electrons are removed they come from the 4s orbitals first Cu 1s2 2s2 2p6 3s2 3p6 3d10 4s1 Ti 1s2 2s2 2p6 3s2 3p6 3d2 4s2 Cu+ 1s2 2s2 2p6 3s2 3p6 3d10 Ti2+1s2 2s2 2p6 3s2 3p6 3d2 Cu2+ 1s2 2s2 2p6 3s2 3p6 3d9 Ti3+1s2 2s 2p6 3s2 3p6 3d1 Ti4+1s2 2s2 2p6 3s2 3p6

COLOURED IONS A characteristic of transition metals is their ability to form coloured compounds Theory 1) Ions with a d10 (full) or d0 (empty) configuration are colourless 2) Ions with partially filled d-orbitals tend to be coloured 3) This is caused by the ease of transition of electrons between energy levels 4) Energy is absorbed when an electron is promoted to a higher level The frequency of light is proportional to the energy difference Colorless: Not transition metal Ions with d10 (full) Cu+,Ag+ Zn2+ d0 (empty) Sc3+ But Ti+4 compounds are white, nevertheless is a transition metal because of Ti+2 and Ti+3 which are colored

There are 5 different orbitals of the d variety 3d ORBITALS There are 5 different orbitals of the d variety xy xz yz x2-y2 z2

COLOURED IONS a solution of copper(II)sulphate is blue because red and yellow wavelengths are absorbed blue and green not absorbed white light