Module 5 (chapter 24) - transition elements

• are all metallic, displaying the typical physical properties of metals • they have high melting and boiling points, shiny in appearance and conduct electricity and heat

• copper, silver, nickel and zinc have been used in coinage for many years • iron is used in construction and the production of tools • copper is used for electrical cables snd water pipes • titanium is known for its great strength and use in aerospace and joint replacement

-the electron configuration of an atom or iron shows the arrangement of electrons in shells and sub shells -electron occupy orbitals in order of increasing energy -the electron configuration of chromium and copper don’t follow the expected principle for placing electron singly in orbitals before pairing -this is due to stability -a half filled d5 sub-shell and a fully filled d10 sub shell give additional stability to atoms chromium (1s2,2s2,2p6,3s2,3p6,3d5,4s1) copper (1s2,2s2,2p6,3s2,3p6,3d10,4s1)

• when forming an atom, the 4s orbital fills before the 3d orbital • when forming an ion, the 4s orbital empties before the 3d orbital

they are d-block elements that form at least one ion with a partially filled d-orbital -you can be a d-block element but not a transition element

scandium only forms Sc3+ ions by loss of two 4s electrons and one 3d electron • it only has one electron in the 3d orbital and therefore its electron configuration becomes 1s2,2s2,2p6,3s2,3p6 • does not have a partially filled d orbital and so isn’t a transition element

• zinc only forms the Zn2+ ion by the loss of two 4s electrons • the electron configuration of Zinc means that when these two electrons are lost it still has a full 3d shell snd so it is not half full.

• they form compounds in which the transition element has different oxidation states • they form coloured compounds • the elements and their compounds can act as catalysts

• transition elements form compounds with more than one oxidation state. • iron forms two chlorides for example (iron(II) chloride and iron(III) chloride • the number of oxidation states increases across the transition elements series to manganese, and then decreases. • all of the transition elements form compounds with an oxidation number of +2, resulting from the loss of two electrons

• compound and ions of transition elements are frequently coloured • potassium dichromate is bright orange • cobalt (II)chloride is pink/purple • nickel sulphate is green • hydrated copper sulfate is blue • the colour of a solution is linked the partially filled d-orbitals of the transition metal ion. the colour can vary with different oxidation states (e.g. iron)

• iron is used to catalyse the hater process which manufactures ammonia • vanadium oxide is used to catalyse the contact process and the production of surfer trioxide from surfer dioxide • nickel is used yo catalyse the hydrogenation of vegetable fats when making margarine • manganese oxide is used to catalyse the decomposition of hydrogen peroxide to form oxygen

• heterogeneous catalysts • some are homogeneous • e.g. reaction between iodide ions and peroxodisulfate ions is catalysed by Fe2+ ions, with reactants and catalyst all in aqueous solution • when the reaction is carried out with a trace of starch, a blue-black colour forms showing the formation of iodine. when catalyst added this precipitate forms much quicker

d-block elements form complex ions -other elements like aluminium can also form complex ions

• when one of more molecules of negatively charged ions bond to a central metal ion. these molecules or ions are known as ligands • the coordination number indicates the number of coordinate bonds attached to the central metal ion

a molecule of ion that donates a paid of electrons to a central metal ion to form a coordinate bond or date covalent bond

• complex ion is enclosed inside square brackets with the overall change of the complex shown outside the square brackets • the overall charge is the sum of the charges on the central metal ion and any ligand present.

-a ligand that is able to donate one pair of electrons to a central metal ion water (neutral) ammonia (neutral) chloride (-1) cyanide (-1) hydroxide (-1)

• ligands that can donate two lone pairs of electrons to the central metal ion, forming two coordinate bonds • the most common are: • 1,2 -diaminoethane (each nitrogen atom donates a paid of electrons to the central metal ion forming a coordinate bond) • ethandioate (each negatively charged oxygen atom donates a lone pair of electrons to the central metal ion)

• depends upon its coordination number. the commonest coordination numbers six and four • many complex ions have a coordination number of six, given an octahedral shape (bond angles of 90 degrees)

• tetrahedral complexes are the most common with bond angles of 109.5 degrees around the central metal ion (e.g. CoCl4 and CuCl4) both 2- • square planar complexes occur in complex ions of transition metals with eight d electrons in the highest energy d sub shell (platinum, palladium and gold) • Im this structure, ligands are arranged at the corners of a square

complex ions can display two types of steriosiomerism • cis/trans isomerism • optical isomerism • the type of stereoisomerism depends on the number and type of ligands that are attached to the central atom plus the shape of the complex • some four coordinate and six coordinate complex ions containing two different types of monodentate ligands show cis-trans isomerism • some six coordinate complex ions containing monodentate and bidentate ligands can show both cis/trans and optical isomerism

• no C=C double bond is required and the shape of the complex holds groups in different orientations about the central metal ion • occurs in square planar and octahedral complexes

• ligands are arranged in the same planes with 90 degree bond angles • in the cis-isomer, the two identical groups are adjacent to each other, whereas in the trans isomer the two identical groups are opposite each other • in the cis isomer the coordinate bonds between the identical ligands are 90 degrees apart vs 180 degrees in the trans-isomer

• complexes containing four of one type of ligand and two as another can show this. the cis isomer have identical glands adjacent to each other, the trans at 180 degrees • octahedral complexes containing bidentate ligands can also shoe cis-trans isomerism • if the other two atoms (not bidentate) are nest to each other is it cis, if they are opposite it is trans