Chapter One · Transition elements · Chemistry. These are 10 questions from the Magmo3 bank on this lesson, from easy to hard. Solve each one, then open "Show answer and explanation". Magmo3 has 98 questions on this lesson, each with an explanation.
Which of the following elements belongs to group VB and has an electronic configuration ending with [Ar], 4s², 3d³?
Correct answer: (A) Vanadium (₂₃V)
Explanation: According to the table of electronic configurations and oxidation states, ₂₃V belongs to group VB and has the configuration [Ar], 4s², 3d³.
A metal ion is drawn into (attracted by) a magnetic field because its d-subshell contains single (unpaired) electrons. This behaviour is described as:
Correct answer: (A) paramagnetism.
Explanation: Species containing unpaired electrons are paramagnetic and are attracted into a magnetic field, whereas fully paired species are diamagnetic.
What is the total number of vertical columns in the d-block of the periodic table, corresponding to the capacity of the d-sublevel?
Correct answer: (B) 10 vertical columns
Explanation: Since the d-sublevel can take up to ten electrons, it contains ten vertical columns.
Iron has atomic number 26. Which of the following correctly represents the electronic configuration of the Fe³⁺ ion?
Correct answer: (B) [₁₈Ar] 3d⁵
Explanation: Iron is [Ar]3d⁶4s²; forming Fe³⁺ removes the two 4s electrons then one 3d electron, giving [Ar]3d⁵.
Which of the following pairs correctly represents the electronic configurations of the Fe²⁺ and Fe³⁺ ions respectively? (₂₆Fe)
Correct answer: (C) [₁₈Ar]3d⁶ and [₁₈Ar]3d⁵
Explanation: Iron loses its two 4s electrons first to give Fe²⁺ [Ar]3d⁶, then a further 3d electron to give Fe³⁺ [Ar]3d⁵.
Which of the following transition elements is found in the earth's crust with a weight percentage of 0.014%?
Correct answer: (D) Chromium (Cr)
Explanation: Chromium (Cr) has a % wt of 0.014.
Copper (₂₉Cu) forms the Cu²⁺ ion. Which choice correctly gives the configuration of this ion together with its magnetic property?
Correct answer: (C) [₁₈Ar]3d⁹; paramagnetic because it has an unpaired electron in the partially filled 3d sub-level.
Explanation: Cu is [Ar]4s¹3d¹⁰; losing two electrons gives Cu²⁺ = [Ar]3d⁹, a partially filled 3d sub-level with one unpaired electron, so the ion is paramagnetic. 3d¹⁰ is the configuration of the atom's d sub-level, not of Cu²⁺.
Which of the following ions has the largest magnetic moment? (Ti = 22, Fe = 26, Co = 27, Ni = 28)
Correct answer: (B) Fe³⁺
Explanation: The magnetic moment increases with the number of unpaired electrons: Fe³⁺ (3d⁵) has 5, Co²⁺ (3d⁷) has 3, Ni²⁺ (3d⁸) has 2 and Ti³⁺ (3d¹) has 1, so Fe³⁺ has the largest moment.
Why is nickel's atomic mass considered abnormal compared to the general trend of increasing atomic mass across the first transition series?
Correct answer: (C) Because nickel has five stable isotopes with an average mass of 58.7 u.
Explanation: The atomic mass increases gradually with atomic number, but nickel is abnormal because it has five stable isotopes with an average mass of 58.7 u.
Regarding the electronic configurations and oxidation states, which transition element exhibits the maximum number of listed common oxidation states?
Correct answer: (C) Manganese (Mn)
Explanation: Looking at the table, Manganese (Mn) has oxidation states 2, 3, 4, 6, 7 (five oxidation states), which is more than Titanium (2, 3, 4), Vanadium (2, 3, 4, 5), or Iron (2, 3, 6).
The first 10 questions in every subject are free, each with an explanation.