C24 Transition Elements Flashcards by Aleesha Khan

Define a transition element

A d block element that forms at least one stable ion with partially filled d subshell

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Where are the transition metals located in the periodic table

In the middle block from Ti to Cu

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What are the 2 elements in the d block that are not considered as transition metals

Scandium and zinc

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Why’s scandium and zinc not considered as transition metals

Scandium only forms Sc^3+, where the d orbitals are empty

Zinc only forms Zn^2+ where the d orbitals are full

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What is the noble gas configuration of chromium

[Ar]4s^1 3d^5

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What’s the noble gas configuration of copper

[Ar]4s^1 3d^10

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Which electrons do transition metals lose first when forming ions

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What are some characteristic physical properties of transition metals

Metallic

High density

High melting and boiling point

Shiny

Good conductors of heat and electricity

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What are the characteristic chemical properties of transition metals

Variable oxidation states —> take part in many redox reactions

Coloured compounds/ions in solution

Good catalysts

Form complex ions

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In in potassium manganate (VII), what’s the oxidation number of Mn

Mn = +7

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What are the 2 main ways in which transition metals act as an effective catalyst

They provide a surface on which reaction can take place

They change oxidation states to form intermediates required for pathways with lower activation energy

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Give some examples of transition metal located and the processes/reactions they catalyse

Iron - haber process

Vanadium (V) oxide - contact process

Nickel - hydrogenation of alkenes

Manganese (IV) oxide decomposition of hydrogen peroxide

Copper sulfate - hydrogen production

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What is a complex ion

Transition metal ion bonded to one or more ligands by coordinate bonds

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Define a ligand

Molecule or an ion that can donate a pair of electrons to the metal to form a coordinate bond

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What’s a coordinate bond

A bond in which one of atom of the atom provides both the electrons required for bonding, also known as dative bonding

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What’s does the coordination number indicate

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

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What’s a mono/unidentate ligand

a ligand that forms one co-ordinate bond to the central metal ion (one lone pair to donate)

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What’s a bidentate ligand

A ligand that forms 2 coordinate bonds to the central metal ion (2 lone pairs to donate)

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What’s a multidentate ligand

A ligand that forms 3 or more coordinate bonds to the central metal ion

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Give some examples of common monodentate ligands

Cl-

H2O

NH3

CN-

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Name the most common bidentate ligand

Ethane-1,2-diamine

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How many coordinate bonds does EDTA^4- form

Six

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EDTA is a chelating agent, what does that mean

EDTA decreases the concentration of metal ions in the solution by binding to them and forming complex ions

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What ion is usually formed when a transition metals act compound is dissolved in water? What shape is it?

Aqua ion

6H2O ligands around the central metal ion

Octahedral complex ion is formed

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If a transition metals act compound ion has 2 ligands, what shape is it usually?

Linear

If a transition metals act compound ion has 4 ligands, what shape is it usually?

Tetrahedral

Name an exception to the general rule that ions with 4 ligands is generally tetrahedral. What shape is it?

Platinum is square planar —> forms cisplatin

What shape is a complex ion if it has 6 ligands

Octahedral

How can complex ions display E/Z or Cis-trans isomerism? What shapes of ions does this apply to

Ligands differ in the way in which they’re arranges in space 2 ligands of the same type can be on the same side of the metal ion(next to each other), which forms the E or Cis-isomer 2 ligands of the same type can be opposite sides of the metal ion(not next to each other), which forms the Z or trans-isomer. Applies to square planar and octahedral complex ions.

What conditions are needed for a complex ion to display optical isomerism

Usually applies to octahedral molecules with 2 or more bidentate ligands, so that the mirror images are non-superimposable

What’s cis-platin used for? Describe its mechanism of action?

Its used as anti-cancer drug It binds to DNA of fast growing cancer cells and prevent cell division, hence reducing the growth of cancer

Which metal ion is present in haem group

Fe^2+

What’s the coordination number of a haem group

What are the ligands in haem group

4 nitrogen forming the porphyrin 1 oxygen 1 globin

Why is CO toxic

CO also coordinately bonds to the Fe^2+, and bonds more strongly to Fe^2+ than O2. Stops O2 from bonding haemoglobin, so O2 cannot be transported around the body

What colour is [Cu(H2O)6]^2+ solution

Pale blue

What colour is [Cu(NH3)4(H2O)2]^2+ solution

Deep blue

What colour is [CuCl4]^2- solution

Yellow

What colour is [Cr(H2O)6]3+ solution

Dark green

What’s precipitation reaction?

A reaction where soluble ions in separate solutions are mixed to form an insoluble compound

What colour is Fe^2+’s aqua ion

Green

What colour is Fe^3+’s aqua ion

Pale brown

What colour is Cr^3+’s aqua ion

Violet

What colour is Mn^2+’s aqua ion

Pink

When Cu^2+ reacts with NH3 or OH^-, what colour is precipitate

Blue

When Fe^2+ reacts with NH3 or OH^-, what colour is the precipitate

Green

When Mn^2+ reacts with NH3 or OH^-, what colour is the precipitate

Brown

When Cr^3+ reacts with NH3 or OH^-, what colour is the precipitate

Green

When Fe^3+ reacts with NH3 or OH^-, what colour is the precipitate

Brown

What colour is MnO4-

Purple

Write a half equation for the reduction of MnO4^- to Mn^2+

MnO4^- + 8H^+ + 5e- ———> Mn^2+ + 4H2O

Why are redox titrations with transition metal compounds said to be self-indicating

They usually involve a colour change as the metal is changing oxidation state Sometimes an indicator is still needed/useful

What colour is CrO7^2-

Orange

What colour is Cr^3+

Green

Write a half equation for the reduction of Cr2O7^2- to Cr^3+

Cr2O7^2- + 14H^+ + 6e^- ———> 2Cr^3+ + 7H2O

Describe how to test for metal ions

Fill half of the test tube with sample Add aq ammonia/NaOH drop by drop Colour of precipitate indicates the ion present

Write the method used to test for ammonium ions

Fill half the test tube with sample Add NaOH and warm gently Smelly gas is produced; damp red litmus paper turns blue

Why does lime water turn milky in the presence of CO2

When CO2 is bubbled in calcium hydroxide (lime water), calcium carbonate precipitate is formed

Carbonate test

Add dilute nitric acid Effervescence (bubbles) = carbonate present

Test for CO2

Bubble through lime water [saturated aq of Ca(OH)2] Lime water turn cloudy —> white precipitate of calcium carbonate forms

Sulfate test

Add barium chloride or barium nitrate BaSO4 forms as a white precipitate as it is very insoluble Ionic equation: Ba^2+(aq) + SO4^2-(aq) —> BaSO4(s)

What’s the ionic equation of the sulfate test

Ba^2+(aq) + SO4^2-(aq) —> BaSO4(s)

Halide test

Silver halides are insoluble in water - Add aq silver nitrate to aq of halide - silver halide precipitate forms Cl^- = white Br^- = cream I^- = yellow - add aq ammonia to test solubility Cl^- = soluble in dilute NH3(aq) Br^- = soluble in conc NH3(aq) I^- = insoluble in conc NH3(aq)

Ammonium ion test

What’s the electron configuration of chromium

24 electrons 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5

What’s the electron configuration of copper

29 electrons 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3s^10

Why do the electron configurations of chromium and copper not follow the expected trend

Because of stability It’s believed that a half-filled d^5 sub-shell and a fully filled d^10 sub-shell give additional stability. To atoms of chromium and copper.

What happens when forming a d-block atom

When forming an atom, 4s orbital fills before the 3d orbitals

What happens when forming a d-block ion

When forming an ion, 4s orbital empties before the 3d orbitals

Why are Sc and Zn not classified as transition elements

They don’t form an ion with a partially filled d-orbital. Sc only forms Sc^3+by loss of 2 4s electrons and 1 3d electron Sc^3+ : 1s^2 2s^2 2p^6 3s^2 3p^6 Zn only forms Zn^2+ by loss of its 2 4s electrons Zn^2+ ; 1s^2 2s^2 3s^2 3p^6 3d^10 Sc^3+ have empty d-orbitals and Zn^2+ have full d-orbitals Sp Sc and Zn do not form ions with partially filled d-orbitals and aren’t therefore classified as elements