5.3.1 transition elements

Question 1

What are the properties of transition metals and their compounds?

Answer 1

Form compounds in which the transition element has different oxidation states.
Form coloured compounds.
Elements and their compounds can act as catalysts.

Question 2

Why do Chromium and Copper not follow the expected principle of placing electrons singly in orbitals before pairing?

Answer 2

Stability- believes that a half-filled d5 sub-shell and a fully filled d10 sub-shell gives additional stability to atoms of chromium and copper.

Question 3

What is the general rule for electron configuration in transition metals?

Answer 3

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

Question 4

What are transition metals?

Answer 4

D-block elements that form at least one ion with a partially filled d-orbital.

Question 5

Why are Zinc and Scandium not transition elements?

Answer 5

Sc3+ ions have empty d-orbitals and Zn2+ ions have full d-orbitals- they don’t form ions with partially filled d-orbitals.

Question 6

What is the electron configuration of Scandium?

Answer 6

Loss of two 4s electrons and one 3d electron-
Sc:1s2,2s2,2p6,3s2,3p6,3d1,4s2.
Sc3+:1s2,2s2,2p6,3s2,3p6.

Question 7

What is the electron configuration of Zinc?

Answer 7

Loss of two 4s electrons-
Zn:1s2,2s2,2p6,3s2,3p6,3d10,4s2.
Zn2+:1s2,2s2,2p6,3s2,3p6,3d10.

Question 8

What are some examples of transition metals being used as heterogeneous catalysts?

Answer 8

The Haber process- manufacture of ammonia from the reaction between nitrogen and hydrogen: N2+3H2->2NH3 (iron catalyst)
The Contact process- production of sulfur trioxide from the oxidation of sulfur dioxide: 2SO2+O2->2SO3 (vanadium oxide V2O5 catalyst)
Hydrogenation of vegetable fats in the manufacture of margarine (nickel catalyst)
Catalytic decomposition of hydrogen peroxide forming oxygen: 2H2O2->2H2O+O2 (manganese oxide,MnO2 catalyst)

Question 9

What are some examples of reactions homogeneously catalysed by transition metals?

Answer 9

Reaction between iodine ions and peroxodisulfate ions: S2O82-+2I->2SO42-+I2 (Fe2+ ions catalyst)
Reaction of zinc metal with acids: Zn+H2SO4->ZnSO4+H2 (Cu2+ ions catalyst)

Question 10

How are complex ions formed?

Answer 10

Formed when one or more molecules or negatively charged ions bond to a central metal ion.

Question 11

What is a ligand?

Answer 11

A ligand is a molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond or dative covalent bond.

Question 12

What is the coordination number?

Answer 12

Indicates the number of coordinate bonds attached to the central metal ion.

Question 13

What is a monodentate ligand?

Answer 13

A ligand that is able to donate one pair of electrons to a central metal ion.

Question 14

What is a bidentate ligand?

Answer 14

A ligand that is able to donate two lone pairs of electrons to the central metal ion, forming two coordinate bonds.

Question 15

What are the most common bidentate ligands?

Answer 15

1,2-diaminoethane
Ethanedioate ion

Question 16

What shape do complex ions with coordination number of six have?

Answer 16

Octahedral

Question 17

What shape do complexes with a coordination number of four have?

Answer 17

Tetrahedral + square planar

Question 18

What are some examples of tetrahedral complexes?

Answer 18

Bond angle of 109.5
[CoCl4]2-
[CuCl4]2-

Question 19

When do square planar complexes occur?

Answer 19

Complex ions of transition metals with eight d-electrons in the highest energy d-sub-shell.
E.g. Platinum(II), Palladium(II), and Gold(III).

Question 20

What is an example of a square planar complex?

Answer 20

[Pt(NH3)2Cl2]

Question 21

What are some examples of octahedral complexes?

Answer 21

[Cu(H2O)6]2+
[Fe(H2O)6]3+

Question 22

What are the cis-trans isomers of [Co(NH3)4Cl2]+?

Answer 22

Cis-isomer: two chloride ligands adjacent to each other with their coordination bonds separated by 90 degrees.
Trans-isomer: two chloride ligands are at opposite corners of the octahedron, with their coordinate bonds 180 degrees apart.

Question 23

What are the cis-trans isomers of [Pd(NH3)2Cl2]?

Answer 23

Cis-isomer: two identical groups are adjacent to each other.
Trans-isomer: two identical groups are opposite each other.