Chapter 5.3-Transition metals Flashcards Preview

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Flashcards in Chapter 5.3-Transition metals Deck (90):

What is a transition metal?

a d-block element that has an incomplete d-sub shell as a stable ion


What members of the period 4 d-block elements are not classed as transition metals because they do not have any ions with partially filled d-orbitals?

-Scandium (only forms the Sc^3+) in which the d-orbitals are empty
- Zinc forms only the Zn^2+ ion, in which the d-orbitals are full


During electron configuration of the period 4 elements the pattern is regular except for what two elements?

-Chromium- the five 3d orbitals and the 4s-orbital all contain one electron, with no orbital being completely filled
-Copper- the five 3d-orbitlas are full, but there is only one electron in the 4s-orbital


What is the electron configuration of chromium?

1s^2, 2s^2 2p^6, 3s^3 3p^6, 4s^2 3d^5


What is the electron configuration of copper?

1s^2, 2s^2 2p^6, 3s^2 3p^6, 4s^1 3d^10


Do the transition metals form positive or negative ions?

-lose electrons to form positive ions


What electrons are lost first when an transition element forms a positive ion?

4s electrons before 3d electrons


What is the electron configuration of Fe^3+?

1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^5


What are the physical properties of transition elements?

- giant metallic lattices when solid
- high densities
- high melting and boiling point
-conduct electricity because of the delocalised electrons


Can transition elements from titanium to copper form stable ions with more than one stable oxidation state?



What ion does all the transition metals form?



what is the name of KMnO4?

potassium manganate(VII)


What is the name of K2Cr2O7?

potassium dichromate(VI)


What is the maximum oxidation state of Mn?



What is the maximum oxidation state of Cr?



What is the colour of KMnO4?



What is the colour of K2Cr2O7?

orange crystalline structure


What are KMnO4 and K2Cr2O7 examples of?

oxidising agents


What is a disproportionation reaction?

one species is both oxidised and reduced in the same chemical reaction


What is the equation for the reaction between copper(I) oxide and hot dilute H2SO4?

Cu20+H2SO4---------Cu+ CuSO4 + H20


What visual changes do you see in the reaction between copper(I) oxide and hot dilute H2SO4?

-brown predicate of copper is formed
- blue solution of copper(II) sulfate


What element undergoes disproportionation in the reaction between copper(I) oxide and hot dilute H2SO4?



What colours do transition elements normally form?

bright colours


What property of the transition elements results in them forming brightly coloured compounds?

-partially filled d-orbitals
-the movement of electrons in the 3d orbital


What colour is scandium when it forms a 3+ ion?



What colours are the three broad regions of the white light spectrum



What determines the colour that the transition metal forms?

-the colour that is observed is a mixture of the wavelengths of light that have not been absorbed


What are the two ways in which transition elements act as a catalyst?

1. provide a surface for the reaction to take place. Reactants are adsorbed onto the surface of the metal and held in place while a reaction occurs. Therefore allows reaction to take place at a lower activation energy.
2. They have many different oxidation numbers. Therefore, they can bind to reactants and form intermediates. The different pathway can have a lower activation energy which increases the rate of reaction


What is the equation for the haber process?

N2(g) +3H2(g)-------2NH3(g)


What transition metal element is used as a catalyst in the haber process and how it acts as a catalyst?

-Fe(s) metal (iron)
- increases the rate of reaction and lowers the temperate required for the reaction to take place


What is the equation for the contact process and what transition metal element is used as a catalyst?

-2SO2 + O2(g)-------- 2SO3(g)
- vanadium(V) oxide V2O5 is used as the catalyst, in which vanadium has the +5 oxidation state


What are two things that sulphuric acid, which is made in the contact process from SO3, is used to make?

- electrolyte in car batteries
- fertilisers


What is the equation for the decomposition of hydrogen peroxide and what transition metal elements is used as the catalyst for this reaction?

- 2H2O2-------2H20+ 02
- manganese (IV) oxide, MnO2
- makes oxygen gas


What is the equation for the reaction where hydrogen is produced and what is the name of the transition metal element that is used to catalyse the reaction?

- Zn(s)+H2SO4------------ZnSO4+ H2(g)
- copper sulphate(CuSO4) is the catalyst


In the hydrogenation of alkenes where hydrogen is added across the C=C double bond, to saturate them, what transition metal element is used to catalyse this reaction?

-lowers the temp and pressure needed for the reaction to take place


What is a complex ion?

transition metal ion bonded to one or more ligands by coordinate bonds (dative covalent bonds)


What is a ligand?

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


What is the coordinate number?

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


What is a coordinate bond?

bond in which one of the atoms provides both electrons for the covalent bond


How do you represent a complex ion?

-square brackets group together the species making up the complex ion
- the overall charge is shown outside the brackets


What is the formula of the complex ion when cobalt(II) salts dissolve in water?



How does water act as a ligand?

-on the oxygen atom there is one lone pair of electrons and this can be donated to form a coordinate bond


What is a monodentate ligand?

Ligand which donates just one pair of electrons to the central metal ion to form one coordinate bond


What is a bidentate ligand?

Ligands which have two pairs of electrons from different atoms to donate to the central metal, forming two coordinate bonds


What are two examples of neutral monodentate ligands?

-H20(oxygen atom supplies the 2 electrons)
-NH3(nitrogen atom supplies the 2 electrons)


What are two examples of negatively charged monodentate ligands?



What is an example of a neutral bidentate ligands?

- ethane-1,2-diamine NH2CH2CH2NH2 (the 2 nitrogen atoms can both donate 2 electrons forming 2 coordinate bonds)


What is an example of a ligand that can form more than 2 coordinate bonds?

-has 6 lone pairs so can form 6 bonds


What is a chelating agent and name an example?

- when a ligand decreases the concentration of the metal ions in solution by binding them into a complex


What is EDTA used in?

- foods
-medical application


What is the most common shape of complex ions?



What are the characteristics of octahedral complexes?

-four of the ligands are on the same plane
-one ligand is above the plane and one ligand is below the plane
-all bonds are separated by 90 degrees and 180 degrees
- six coordinate bonds are made


What two compounds form octahedral complexes?

-water (H20)
-ammonia (NH3)
-this is be cause they are similar sizes and the right size to fit six around a metal ion


What compound forms an octahedral complex and has multidentate bonds?



What are complex ions which have four-fold coordination?

- four coordinate bonds are made
-tetrahedral shape or planar shape


What is an example of a ligand that forms a tetrahedral shape when bonded to a transition metal element?

-Chloride ligands
-They are so large that only four can fit around a transition metal ion
-Examples are [CuCl4]^2- and [CoCl4]^2-


What is a square planar complex?

-the four monodentate ligands arrange themselves in the same plane as the metal atom


What is a stereoisomer?

species with the same structural formula but with a different arrangement of atoms in space


In complex ions, how do cis isomers arise?

-the pair of different atoms are next to each other
- the two ligands are at 90 degrees to one another


in complex ions, how do trans isomers arise?

-the pair of different isomers are at opposite corners of the octahedron
-the two ligands are at 180 degrees to one another


What are the two colours of the complex ion [Co(NH3)4Cl2]^2+ which has cis and trans isomerism?

-cis is purple
-trans is green


What is an example of a square planar shape which exhibits cis-trans isomerism?

-platinum complex [PtCl2(NH3)2]
-Cis-platin is the cis isomer
-trans-platin is the trans isomer


How does Cis-plating prevent cancers from growing?

-cancer is spread throughout an organism by cell division of a cancerous cell that can reproduce itself
- Cis-platin works by binding to the DNA, preventing cell division from taking place and leading to the death of the cell


What are the side effects of using Cis-plating to treat cancer?

-hair loss


Can both isomers of the platinum complex [PtCl2(NH3)2] be used for cancer treatment?

-the trans-platin isomer is less effective and more toxic


What new generation of drug has been introduced to battle cancer at lower doses and with less severe side-effects?



What type of complexes have optical isomers?

octahedral complexes with multidentate ligands


What is a optical isomer?

non-superimposable mirror images of each other


What octahedral complexes forms optical isomers?

-a complex with 3 bidentate ligands e.g. [Ni(en)3]^2+
- a complex with 2 bidentate ligands and 2 monodentate ligands e.g. [Co(en)2Cl2]
- a complex with a hexadentate ligand e.g. [Cu(EDTA)]21


What is a ligand substitution reaction?

a reaction in which one ligand in a complex ion is replaced by another ligand


What colour is aqueous copper(II) [Cu(H20)6]^2+ in solution?

pale blue solution


When you add small amounts of ammonia(NH3) to the copper(II) [Cu(H20]6]^2+, what happens?

-ligand substitution reaction
-ammonia acts as a base accepting protons from the water, and forming copper hydroxide precipitate(blue solid) [Cu(OH)2]
-[Cu(H2O)6]^2+(aq) +2NH3(aq)------[Cu(OH)2(H20)4](s) + 2NH4^+(aq)


What happens when you add excess ammonia to copper (II)[Cu(H20]6]^2+?

-the copper hydroxide precipitate dissolves and the ammonia replaces the water as ligands
- [Cu(H20)6]^2+(aq)+4NH3(aq)-----[Cu(NH3)4(H2O)2]^2+(aq) +4H20(l)


What colour is the solution containing the [Cu(NH3)4(H20)2]^2+ complex ion?

deep blue solution(s)


What happens when aqueous copper(II)[Cu(H20]6]^2+ ions reacts with concentrated HCL?

-ligand substitution reaction
- pale blue solution initially forms a green solution before finally turning yellow. This is because the [Cu(H20]6]^2+ is pale blue and when it mixes with the copper chloride which is yellow it turns green.
-equilibrium reaction


What is the equation fort he reaction between aqueous copper(II)[Cu(H20]6]^2+ ions reacts with concentrated HCL?

[Cu(H20]6]^2+(aq) + 4Cl^-(aq)------- [CuCl4]^2-(aq) +6H20 (l)


Why does the number of ligands reduce in the reaction between[Cu(H20]6]^2+ and concentrated HCL, which forms [CuCl4]^2-(aq) ?

-the chloride ligands are larger than the water ligands and have stronger repulsions, so fewer chloride ligands can fit around the central metal ion


What colour are aqueous chromium (III) complex ions, [Cr(H20)6]^3+?

grey green or dark green colour


What happens when [Cr(H20)6]^3+ reacts with dilute ammonia (small amount) (NH3) and what is the equation?

-ammonia acts as a base
- forms a chromium hydroxide precipitate(green solid) by removing protons from the water ligands
-[Cr(H20)6]^3+(aq) +3NH3(aq)---------{Cr(H20)3(OH)3](s) +NH4^+(aq)


What happens when excess ammonia reacts with [Cr(H20)6]^3+?

-some of the green precipitate re-dissovles to form a dark green solution
-water ligands are replaced by ammonia
-[Cr(H20)6]^3+ + 6NH3----------[Cr(NH3)6]^3++6H20


What is haemoglobin's function?

-haemoglobin is found in red blood cells
- it is a complex protein made of four polypeptide chains
-each chain contains a non-protein group called a haem group which has Fe^2+ at its centre
-oxygen can reversibly bind to the Fe^2+
-when oxygen binds to haem group the haem group is red in colour


Describe the structure of haemoglobin in terms of its coordinate bonds

-four coordinate bonds between the Fe^2+ and the nitrogen atoms in the haem group
-1 coordinate bonds is formed to the protein globin
-1 coordinate bond can form to an oxygen molecule, which is then transported


Why is carbon monoxide dangerous?

-CO can bind to haemoglobin at the same place as oxygen.
-binds more strongly than oxygen
-irreversible reaction-once the haem group is binded to CO than the haemoglobin cant be used again.


How is the reaction between CO and oxygen with haemoglobin a ligand substitution reaction?

-CO molecules can replace oxygen molecules in haemoglobin


What is a precipitation reaction?

soluble ions are mixed together to produce an insoluble compound(precipitate) which settles out of solution as a solid


What are the equations and what do you observe when Cu^2+(aq) reacts with NaOH and ammonia?

-Blue gelatinous precipitate formed
-[Cu(H20)6]^2+(aq) + 2OH^-(aq)----[Cu(OH)2(H20)4](s) +2H20
-Blue gelatinous precipitate formed, which re-dissolves to a blue solution
-[Cu(H2O)6]^2+(aq) + 2NH3(aq)-----[Cu(OH)2(H2O)4](s) + 2NH4^+(aq)


What are the equations and what do you observe when Fe^2+(aq) reacts with NaOH and ammonia?

-Pale green solution containing Fe^2+(aq) forms a green precipitate, turning a rusty brown colour at its surface on standing in air
-dark green precipitate formed
- [Fe(H20)6^2+(aq) +2NH3(aq)----[Fe(OH)2(H2O)4](s) +2NH4^+(aq)


What are the equations and what do you observe when Fe^3+(aq) reacts with NaOH and ammonia?

- pale yellow solution containing Fe^3+(aq) forms a rusty brown precipitate (iron(III) hydroxide)
-Fe^3+(aq)+ 3OH^-(aq)-----Fe(OH)3(s)
-rusty brown precipitate formed
-[Fe(H2O)6]^3+(aq) + 3NH3(aq)------[Fe(OH)3(H2O)3](s) +3NH4^+


What are the equations and what did you observe when Mn^2+(aq) reacts with NaOH and ammonia?

-brown precipitate forms, which darken in air as it oxidises [Mn(H2O)6]^2+(aq) +2OH^-(aq)-----[Mn(OH)2(H2O)4](s) +2H2O
-Brown precipitate forms, which darkens in air as it oxidises
-[Mn(H20)6]^2+(aq) + 2NH3(aq)-----[Mn(OH)2(H2O)4](s) +2NH4^+(aq)


What are the equations and what do you observe when Cr^3+(aq) reacts with NaOH and ammonia?

-green precipitate forms, which will be then re-dissolved in excess hydroxide
-[Cr(H2O)6]^3+(aq) +3OH-(aq)----[Cr(OH)3(H2O)3](s)+3H2O then
[Cr(OH)3(H20)3](s) +3OH^-(aq)-----[Cr(OH)6]^3-(aq) +3H2O
-green precipitate forms, which will re-dissovle if excess ammonia is added
-[Cr(H2O)6]^3+(aq) +3NH3(aq)----[Cr(OH)3(H2O)3](s) +3NH4^+(aq) then
[Cr(OH)3(H20)3](s) + 6NH3(aq)------[Cr(NH3)6]^3+(aq) +3H20 + 3OH^-(aq)