DM 4 - Inorganic Chemistry and the Periodic Table Flashcards

1
Q

What are transition metals?

A

Transition metals are d-block elements that can form one or more stable ions which have an incomplete d-subshell

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2
Q

Where are the electronic configurations of chromium and copper?

A

The electron configurations of chromium and copper are exceptions to the rule of filling up subshells:
Chromium: 1s2 2s2 2p6 3s2 3p6 3d5 4s1
Copper: 1s2 2s2 2p6 3s2 3p6 3d10 4s1

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3
Q

What are the common oxidation states of copper and iron?

A
  • Copper normally has an oxidation state of one (Cu+) or two (Cu 2+)
  • Iron normally has an oxidation state of two (Fe 2+) or three (Fe 3+)
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4
Q

What are the colours of these ions (if any)?
Cu+, Cu 2+, Fe 2+, Fe 3+

A

Cu +: colourless
Cu 2+: blue
Fe 2+: green
Fe 3+: yellow/brown

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5
Q

Why do transition metals have variable oxidation states?

A

The d subshell has a lot of stable states so different numbers of electrons can be lost to produce ions that are all stable

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6
Q

What is a ligand?

A

A ligand is an electron donor that forms a dative covalent/coordinate bond with a central metal ion/atom

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7
Q

What is a complex ion?

A

A central metal ion bonded via coordinate bonds to electron donors (ligands) that are either negatively charges or possess a lone pair of electrons

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8
Q

What is a monodentate, bidentate and polydentate ligand?

A

Monodentate: Ligand forms 1 coordinate bond to the central metal ion, donating 1 electron pair
Bidentate: Ligand forms 2 coordinate bonds to the central metal ion, donating 2 electron pairs
Polydentate: Ligand forms many coordinate bonds to the central metal ion, donating many electron pairs

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9
Q

What is a ligand substitution?

A

A ligand substitution reaction is where one ligand in a complex ion is replaced by another ligand

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10
Q

What is a precipitation reaction?

A

When two ionic aqueous solutions react together to form an insoluble ionic solid, this is known as a precipitate

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11
Q

How does iron(II) and iron(III) react with NaOH in a precipitation reaction?

A

Fe 2+(aq) + 2OH-(aq) –> Fe(OH)2(s)
green solution green precipitate
Fe 3+(aq) + 3OH-(aq) –> Fe(OH)3(s)
yellow solution orange/brown precipitate

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12
Q

How does copper(II) react with NaOH in a precipitation reaction?

A

Cu 2+(aq) + 2OH-(aq) –> Cu(OH)2(s)
blue solution blue precipitate

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13
Q

Why do transition metals make good homogeneous catalysts?

A
  • Since transition metals have various oxidation states, they make good homogeneous catalysts
  • This is because they are able to oxidise and reduce reactants and intermediates to form the desired product(s)
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14
Q

Why do transition metals make good heterogeneous catalysts?

A

Using the 3d and 4s electrons of the atoms on the catalyst surface, transition metals can form weak bonds with reactants which make them more reactive

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15
Q

Why are transition metal complexes often coloured?

A
  • When light is incident on an object, some is absorbed
  • It will only be absorbed if its energy equals the difference in energies between two energy levels of the atom
  • If it does, an electron becomes excited and is raised to a higher energy level
  • The difference in energy between the two energy levels is often equivalent to the wavelengths/frequencies of the visible region of the electromagnetic spectrum
  • Therefore transition metal complexes often appear coloured
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