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Chemistry > Chapter 28 Transition Elements > Flashcards

Chapter 28 Transition Elements Flashcards

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1
Q

Define transition element.

A
  • d-block element
  • which forms one or more stable ions
  • with incomplete d-orbitals (therefore, 3d^0 & 3d^10 are excluded)
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2
Q

What are the 5 d-orbitals?

A
  • x^2 - y^2
  • xy
  • yz
  • xz
  • z^2
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3
Q

Sketch the shape of a 3dxy orbital & 3dz^2 orbital.

A
  • refer to slides
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4
Q

State the properties of transition elements.

A
  • variable oxidation states
  • behave as catalysts
  • form complex ions
  • form coloured compounds
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5
Q

Why do transition elements have variable oxidation states?

A
  • Easier to remove the third electron compared with the 1st & 2nd.
  • 4s orbital & the 3d orbitals have a small energy difference.
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6
Q

Why are Scandium & Zinc not transition metals?

A
  • Sc3+ = 3d^0
  • Zn2+ = 3d^10
  • Both ions have no incomplete d-orbitals.
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7
Q

How do we predict oxidation states?

A
  1. Remove all electrons from 4s orbital. Therefore, all transition metals have a minimum of +2 oxidation state (4s^2).
  2. Remove unpaired electrons from 3d orbital.
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8
Q

State the electronic configuration & oxidation states for Titanium (Ti)
(Ar = 22).

A
  • Ti: [Ar] 4s2 3d2
  • Oxidation states: +2, +3, +4
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9
Q

State the electronic configuration & oxidation states for Chromium (Cr)
(Ar = 24).

A
  • Cr: [Ar] 4s1 3d5
  • Oxidation states: +2, +3, +4, +5, +6
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10
Q

State the exception for Chromium (Cr), which cannot have a +1 oxidation state.

A
  • Not stable.
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11
Q

State the electronic configuration & oxidation states for Manganese (Mn)
(Ar = 25).

A
  • Mn: [Ar] 4s2 3d5
  • Oxidation states: +2 to +7
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12
Q

Why can’t we have Mn7+?

A
  • Mn7+ cannot exist as a monoatomic ion. It has to form a polyatomic ion. Hence, MnO4-
  • Because across the period, shielding effect remains constant, nuclear charge increases, & nuclear attraction increases.
  • Not stable.
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13
Q

State the electronic configuration & oxidation states for Iron (Fe)
(Ar =26).

A
  • Fe: [Ar] 4s2 3d6
  • Oxidation states: +2 to +6
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14
Q

State the electronic configuration & oxidation states for Cobalt (Co)
(Ar = 27).

A
  • Co: [Ar] 4s2 3d7
  • Oxidation states: +2 to +5
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15
Q

State the electronic configuration & oxidation states for Copper (Cu)
(Ar = 29).

A
  • Cu: [Ar] 4s2 3d7
  • Oxidation states: +1, +2
  • Copper is an exception to the rules because it can exist as +1.
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16
Q

Why are transition metals good catalysts?

A
  • They have variable oxidation states.
  • Can form complexes - easily change to various oxidation states by gaining or donating electrons from reagents within the reaction.
  • Good catalytic site - substances can be adsorbed onto their surface & activated.
17
Q

Define complex.

A
  • central metal ion
  • surrounded by ligands
  • by forming dative bond(s)
18
Q

Define ligand.

A
  • species with lone pair
  • forms dative bond
  • with central metal ion
19
Q

Draw the [Fe(H2O)6]2+ complex ion.

A
  • 6 H2O molecules
  • 2 lone pairs of electrons on each oxygen atom in each H2O molecule
  • 6 dative bonds
  • charge = 2+
  • refer to class notes
20
Q

Name some common ligands.

A
  • H2O
  • Cl-
  • NH3
  • CN-
  • OH-
  • CH3OH
  • CH3NH2
21
Q

Relationship between relative formula mass (Mr) & number of ligands formed.

A
  • Greater Mr, fewer ligands.
  • Mr H2O = 18, 2 to 6 ligands
  • Mr NH3 = 17, 2 to 6 ligands
  • Mr OH- = 26, 4 to 6 ligands
  • Mr CN- = 26, 4 to 6 ligands
  • Mr Cl- = 35.5, up to 4 ligands
22
Q

How do complexes form? Use Fe2+ & H2O as an example.

A
  • Electronic configuration of Fe2+: [Ar] 3d6
  • Fe2+ has 4 unpaired electrons in the 3d orbital.
  • When H2O approaches, the 6 lowest orbitals from subshells 4s, 4p & 4d hybridise.
  • The lone pairs of electrons from 6 H2O molecules go into the 6 hybridised orbitals (that are of the same energy level).
23
Q

Define monodentate ligand.

A
  • 1 ligand uses
  • 1 lone pair to form
  • 1 dative bond with central metal ion.
  • E.g. NH3 (has 1 lone pair)
24
Q

Define bidentate ligand.

A
  • 1 ligand uses
  • 2 lone pairs to form
  • 2 dative bonds with central metal ion
  • Lone pairs must have a gap of more than 1 atom between each other.
25
Q

Examples of bidentate ligands.

A
  • -OOCCOO- (diethanoate ion)
  • HOCH2CH2OH (ethylene glycol)
  • H2NCH2CH2NH2 (ethylene diamine)
26
Q

Draw the [Fe(HOCH2CH2OH)3]2+ ion.

A
  • refer to class discussion
27
Q

Define coordination number.

A
  • Number of coordinate bonds surrounding the metal.
28
Q

[Fe(CN-)6]3-:
- oxidation state of metal?
- no. of ligands?
- type of ligand?
- coordination number?
- shape + angle?
- is it coloured? why?

A
  • Oxi. state = +3
  • No. of ligands = 6
  • Type of ligand = monodentate
  • Coordination number = 6
  • Shape + angle = octahedral & 90°
  • Coloured? = Yes. Fe3+ has incomplete d-orbitals.
29
Q

Which Group & which metals forms complex ions with a square planar shape?

A
  • Group 10
  • Nickel, palladium, platinum
  • Because 4 bond pairs & 2 lone pairs.
30
Q

[Cu(H2O)6]3+:
- oxidation number of metal
- no. of ligands
- type of ligands
- coordination number
- shape + angle
- is it a coloured complex? explain
- draw structure

A
  • oxi no. - +3
  • no. of ligands - 6
  • type of ligand - monodentate
  • coordination number - 6
  • shape + angle: octahedral, 90°
  • Yes. Because Cu3+ has an incomplete d-orbital.
  • Refer to WS 31.1
31
Q

[Ni(CN)4]2-:
- oxidation number of metal
- no. of ligands
- type of ligands
- coordination number
- shape + angle
- is it a coloured complex? explain
- draw structure

A
  • oxi no. - +2
  • no. of ligands - 4
  • type of ligand - monodentate
  • coordination number - 4
  • shape + angle: square planar, 90°
  • Yes. Because Ni2+ has an incomplete d-orbital.
  • Refer to WS 31.1
32
Q

[Co(NH2CH2CH2NH2)3]2+:
- oxidation number of metal
- no. of ligands
- type of ligands
- coordination number
- shape + angle
- is it a coloured complex? explain
- draw structure

A
  • oxi no. - +2
  • no. of ligands - 3
  • type of ligand - bidentate
  • coordination number - 6
  • shape + angle: octahedral, 90°
  • Yes. Because Co2+ has an incomplete d-orbital (3d7).
  • Refer to WS 31.1
33
Q

Explain why transition elements behave as catalysts. (2)

A
  • more than 1 (stable) oxidation state
  • empty d-orbitals can form dative bonds with ligands

Chemistry (13 decks)

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