Transition elements Introduction

1. Transition elementsIntroduction Members • Definition • Transition elements are elements with partially filled d-orbital The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

2. Transition elementsIntroduction • (b) Paramagnetism • Transition metals are weakly attracted by a magnet due to presence of unpaired electrons. Those that are strongly attracted by a magnet are said to be ferromagnetic, e.g., iron, cobalt and nickel. • . • Properties of transition metals • (a) Physical properties • They are hard metals, with high melting and boiling points due to strong interatomic bonding that involves the participation of both the 4s- and 3d-electrons. They are good conductors of heat and electricity due a big number of delocalized electrons in s- and d- orbitals. • They have high densities are due to small atomic radii and high atomic masses. The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

3. Transition elements • Reason for formation of colored ions • Transition metals form colored ions because electron transitions in their ions or complexes produce or absorb radiations within the visible part of the spectrum. • (c) Formation of colored ions • Most compounds and complexes of transition metal ions are colored, with the actual color depending on the oxidation states of the central ions. • For example • Fe2+ is green • Fe3+ is brown The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

4. Transition elements • The more you revise the more you are likely to succeed. • (d) Complex ions formation • Transition metals form many complex ions; e.g. [Fe(CN)6]3-. The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

5. Transition elements • Factors that facilitates formation of complexes • The ions of transition elements have a high charge density to attract electrons. • The ions of transition elements have vacant d-orbitals that can accommodate electron pairs to form dative bonds • Definition • A complex ion • is the one that contains a central ion linked to other atoms, ions or molecules called ligands through dative bonds.  • A dative bond • is a covalent bond in which the shared electron pair is contributed by a single atom. The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

6. Transition elements • Trial 1 • Determine the oxidation states and co-ordination numbers of the central metal ions in each of the following complexes. • A coordination number • is number of ligands that form dative bonds with the central ions. For example; [Fe(CN)6]3- has a coordination number 6 The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

7. Transition elements • (b) Fe(CN)63- and [CuCl4]2- are complexes formed by iron and copper respectively. • State; • The oxidation states of; • Iron • Copper • The co-ordination numbers of; • Iron • Copper (2marks) • Trial 2 • One of the properties of transition metals is complex ion formation • (a)(i) Define the term ‘complex ion’. • (2 marks) • (ii) Explain why transition metals form complexes (2 marks) The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

8. Transition elements • (f) Catalytic activity • Transition metals have high catalytic activity. The transition metals use their variable oxidation states to provide alternative mechanisms to the reactions that require low activation energies thus speeding up chemical reactions. • (e) Variable oxidation states •  Most transition metals exhibit variable positive oxidation states. For example iron has Fe2+ and Fe3+. • Transition metals form variable oxidation state because they have many electron in outermost shell with almost the same energy The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

9. Transition elements • General properties • (g) The formation of interstitial compounds • The sizes of transition metal atoms and their crystal structures are such that small atoms like hydrogen, boron, carbon and nitrogen can occupy the spaces within the crystal and form interstitial compounds. No definite chemical formula can be attached to these substances since they are non stoichiometric. • General properties • (f) Catalytic activity • Definition • A catalyst is a substance that speeds up a chemical reaction without taking part in the reaction. Example: • V2O5, in Contact process The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug

10. Transition elements • 1. Scandium • It is the first element in the first transition series. Apart from having partially filled d-orbital; it show no other property of transition elements. It has a fixed oxidation state of +3.  • General properties • Trial 3 • With reference to transition metals, explain what is meant by the following: • Complex-ion, (5 marks) • Catalytic activity, (3 marks) • Colored ion formation. (5 marks) The best secondary school that teaches sciences best is The Science Foundation College For more exams browse: digitalteacthers.co.ug, E-mail: info@digitalteachers.co.ug