Chapter 24 - Transition Elements

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25 Terms

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d-block elements

their highest energy/outer shell electron occupy the d-sub shell/d-orbitals

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transition element

a d-block element that can form an ion with an incomplete/partially filled d-sub shell

-from Ti to Cu

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EXCEPTIONS of transition elements

Sc = can only ion form Sc3+ which contains an empty d-sub shell

Zn = can only form Zn2+ which contains a completely filled d-sub shell

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properties of transition elements 1)

form compounds where it has variable oxidation states

-a species containing a transition metal in its highest oxidation state is a strong oxidising agent

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properties of transition elements 2)

form coloured compounds

-colour depends on oxidation state of metal which is caused by partially filled d-orbitals

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properties of transition elements 3)

elements + compounds act as catalysts

-provide a surface which reaction can take place on
-change oxidation states to form intermediates for lower activation energy pathways

examples = Fe in Haber Process, Ni in hydrogenation of alkenes

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complex ion

a transition metal ion bonded to one or more ligands by coordinate bonds

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ligand

a molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond

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coordinate bond

a bond in which one of the atoms provides both electrons for the covalent bond (dative covalent bond)

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coordination number

the number of coordinate bonds formed between a central metal ion and its ligands

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<p>writing complex ions formulae </p>

writing complex ions formulae

-square brackets [ ] used to write all parts of complex ion

-round brackets ( ) used to contain ligands that are molecular OR if there is more than 1 type of ligand present

-overall charge written outside of square brackets

-anions or cations that neutralise the charge of ion are not included

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monodentate ligand

donates 1 pair of electrons to central metal ion to form 1 coordinate bond

examples = Cl-, H2O, NH3, CN-

<p>donates <span style="color: green"><strong>1 </strong></span><strong>pair of electrons</strong> to central metal ion to form <span style="color: green"><strong>1 </strong></span><strong>coordinate bond</strong></p><p>examples =<strong> Cl-, H2O, NH3, CN-</strong></p>
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bidentate ligand

donates 2 pairs of electrons to central metal ion to form 2 coordinate bonds

example = ethane-1,2-diamine (en)

<p>donates<strong> </strong><span style="color: blue"><strong>2 </strong></span><strong>pairs of electrons</strong> to central metal ion to form<strong> </strong><span style="color: blue"><strong>2 </strong></span><strong>coordinate bonds </strong></p><p>example = ethane-1,2-diamine (<strong>en</strong>)</p>
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multidentate ligand

donates 3 or more pairs of electrons to central metal ion to form 3 or more coordinate bonds

example = EDTA

<p>donates<span style="color: purple"> <strong>3 or more</strong></span><strong> pairs of electrons </strong>to central metal ion to form <span style="color: purple"><strong>3 or more</strong></span><strong> coordinate bonds</strong></p><p>example = <strong>EDTA</strong></p>
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shapes of complex ions -octahedral (DRAW [Mn(H2O)6]2+)

-6 coordinate bonds - coordination number = 6

-4 of the ligands are on the same plane (dashed + wedged)

-1 ligand is above the plane and 1 is below the plane (straight)

-bond angle = 90

-the oxygen atom in H2O ligand must be coordinated to central metal ion as oxygen supplies pair of electrons

<p>-<strong>6</strong> coordinate bonds - coordination number =<strong> 6</strong></p><p>-<strong>4</strong> of the ligands are on the <span style="color: green">same plane</span> (dashed + wedged)</p><p>-<strong>1 </strong>ligand is <span style="color: blue">above </span>the plane and <strong>1</strong> is <span style="color: red">below </span>the plane (straight)</p><p>-bond angle =<strong> 90</strong></p><p>-the <strong>oxygen atom in H2O ligand</strong> must be <strong>coordinated to </strong>central metal ion as <strong>oxygen supplies pair of electron</strong>s </p>
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shapes of complex ions -tetrahedral (DRAW [CuCl4]2-)

-4 coordinate bonds - coordination number = 4

-complex ions containing chloride ions tend to be tetrahedral

-bond angle = 109.5

<p>-<strong>4 </strong>coordinate bonds - coordination number =<strong> 4</strong> </p><p>-complex ions containing <strong>chloride ions</strong> tend to be tetrahedral </p><p>-bond angle =<strong> 109.5</strong></p>
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shapes of complex ions -square planar (DRAW [Pt(NH3)4]2+)

-4 coordinate bonds - coordination number = 4

-complex ions containing Pt, Pd, Au and Ni

bond angle = 90

<p>-<strong>4</strong> coordinate bonds - coordination number =<strong> 4</strong></p><p>-complex ions containing <strong>Pt, Pd, Au and Ni </strong></p><p>bond angle = <strong>90</strong></p>
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stereoisomers

compounds that have the same structural and molecular formula but different arrangement of atoms in space

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cis-trans isomerism (diagram= square planar)

-occurs in square planar + octahedral complexes

-cis or Z = 2 ligands of the same type are adjacent and on the same side of the metal ion - are 90 degrees apart

-trans or E = 2 ligands of the same type are on opposite sides - are 180 degrees apart

<p>-occurs in <strong>square planar + octahedral</strong> complexes</p><p>-<span style="color: blue"><strong>cis or Z</strong></span> = 2 ligands of the same type are <strong>adjacent</strong> and <strong>on the same side </strong>of the metal ion - are <strong>90 degrees apart</strong></p><p>-<span style="color: red"><strong>trans or E</strong></span> = 2 ligands of the same type are <strong>on opposite sides</strong> - are <strong>180 degrees apart</strong></p>
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cis-trans isomerism in OCTAHEDRALS -DRAW

-monodentate ligands

-mixture of monodentate + bidentate ligands

<p>-monodentate ligands</p><p>-mixture of monodentate + bidentate ligands </p>
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optical isomerism

molecules that are non-superimposable images of each other (mirror images that will not look the same when laid on top of another)

-exists in octahedral complexes with multidentate ligands

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CONDITIONS for optical isomerism

1) complex with 3 molecules/ions of a bidentate ligand

2) complex with 2 molecules/ions of a bidentate ligand AND 2 molecules/ions of a monodentate ligand

3) complex with 1 hexadentate ligand

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uses of cis-platin

-used as an anti-cancer drug

-binds to the DNA of fast growing cells and prevents cell division, reducing growth of cells and can lead to apoptosis

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haemoglobin

-has 4 haem groups with Fe2+ in centre

-in 1 haem = 6 coordinate bonds with central Fe2+ ion - 4 with nitrogen atoms, 1 with globin and 1 with oxygen

-shape = octahedral

-temporary ligand = oxygen

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haemoglobin + carbon monoxide

-carbon monoxide coordinately bonds with the Fe2+ and forms stronger bonds than oxygen

-so if oxyhaemoglobin already formed, carbon monoxide can replace oxygen and form carboxyhaemoglobin = ligand substitution

-stops oxygen from bonding to haemoglobin so cannot be transported around the body