transition metals & coordinate chemistry

Which of the transition metals is the best conductor of heat and electric current?

• copper

• silver

• gold

• titanium

• tungsten

Answer explanation

Silver is the best conductor of heat and electric current among transition metals due to its high electron mobility and low resistivity, making it superior to copper, gold, titanium, and tungsten.

Why do transition metals show a lot of chemical similarities within a given period?

• The valence s and p electrons affect their chemistry more so than the inner d and f electrons, which do not participate in bonding as easily.

• The number of electrons within a given period varies only slightly and is sometimes identical because these metals have more than one ionic form.

• All elements in a given period, including the representative elements, have a lot of chemical similarities due to the gradual increase in atomic number

• The transition metals always fill their s and p orbitals first before filling their d orbitals, which affects their chemistry.

• None of the answers are right

Answer explanation

The correct choice highlights that the valence s and p electrons are more influential in chemical bonding than the inner d and f electrons, which do not participate as readily, leading to similarities among transition metals.

What is the maximum oxidation state expected for vanadium?

• +5

• +8

• +6

• +4

• +3

Answer explanation

Vanadium can exhibit oxidation states from -1 to +5. The maximum oxidation state is +5, which occurs in compounds like vanadium pentoxide (V2O5). Therefore, the correct answer is +5.

What is the electron configuration of the Mn(II) ion?

• [Ar] 4s²3d⁵

• [Ar] 3d⁵

• Ar] 4s¹3d⁵

• [Ar] 4s²3d³

• none of these

Answer explanation

The Mn(II) ion has lost two electrons from its neutral state. The electron configuration of neutral Mn is [Ar] 4s² 3d⁵. Removing two electrons from the 4s subshell gives [Ar] 3d⁵, which is the correct configuration for Mn(II).

What is the electron configuration of the Sc(I) ion?

• [Ar] 4s¹4d¹

• [Ar] 4s¹3d¹

• [Ar] 3s¹3d¹

• [Ar] 4s²

• [Ar] 3d²

Answer explanation

The Sc(I) ion has lost one electron from its neutral state. Scandium's neutral electron configuration is [Ar] 3d² 4s². Removing one electron from the 4s subshell gives [Ar] 3d², making it the correct answer.

What is the electron configuration of the Ni(II) ion?

• [Ar] 4s²3d⁶

• [Ar] 4s¹3d⁷

• [Ar] 4s²3d⁸

• [Ar] 3d⁸

• none of these

Answer explanation

Nickel (Ni) has an atomic number of 28, with a neutral configuration of [Ar] 4s² 3d⁸. For Ni(II), two electrons are removed from the 4s subshell, resulting in [Ar] 3d⁸ as the correct electron configuration.

Which of the metal ions in the following complex ions has a d⁵ electron configuration?

• V(H₂O)₆²⁺

• Mo(NH₃)₆³⁺

• Co(CN)₄^–

• Fe(CN)₆^3–

• RhCl₆^4–

Answer explanation

The ion Fe(CN)6^3– contains Fe in the +3 oxidation state, which has a d⁵ electron configuration (3d⁵). Other options do not have a d⁵ configuration.

What are the oxidation numbers of each central metal atom in the following coordination compounds?

K₃[Fe(CN)₆], [Cr(NH₃)₄Br₂]Br, [Ni(H₂O)₆]Cl₂, Na₂[TaF₇]

• 3, 3, 3, 5

• 3, 3, 2, 7

• –3, 3, 2, 5

• –3, 1, 2, 5

• 3, 3, 2, 5

Answer explanation

In K3[Fe(CN)6], Fe has an oxidation state of +3. In [Cr(NH3)4Br2]Br, Cr is +3. In [Ni(H2O)6]Cl2, Ni is +2. In Na2[TaF7], Ta is +5. Thus, the oxidation numbers are 3, 3, 2, 5, matching the choice 3, 3, 2, 5.

Ethylenediamine (en) is a bidentate ligand. What is the coordination number of cobalt in [Co(en)₂Cl₂]Cl?

• 4

• 5

• 6

• 7

• 8

Answer explanation

In [Co(en)2Cl2]Cl, cobalt is coordinated by 2 bidentate ethylenediamine ligands (2x2=4) and 2 chloride ions. Thus, the total coordination number is 4 + 2 = 6, making the correct answer 6.

Which of the following coordination compounds will form a precipitate when treated with an aqueous solution of AgNO₃?

• [Cr(NH₃)₃Cl₃]

• [Cr(NH₃)₆]Cl₃

• [Cr(NH₃)Cl]NO₃

• Na₃[Cr(CN)₆]

• Na₃[CrCl₆]

Answer explanation

[Cr(NH3)6]Cl3 will dissociate in solution to release Cl-, which can react with Ag+ from AgNO3 to form AgCl precipitate. The other compounds do not release Cl- in a way that would lead to precipitation.