Which of the following ions has the maximum magnetic moment?
A. Mn²⁺
B. Fe²⁺
C. Ti²⁺
D. Cr²⁺

To determine which of the given ions has the maximum magnetic moment, we need to consider their electron configurations and the number of unpaired electrons. Magnetic moments in ions are primarily determined by the presence of unpaired electrons because they contribute to the magnetic properties of the ion.

Let's analyze each of the ions:

A. Mn^+2 (Manganese ion with a +2 charge):
The electron configuration of Mn^+2 is [Ar] 3d^5. It has 5 unpaired electrons.

B. Fe^+2 (Iron ion with a +2 charge):
The electron configuration of Fe^+2 is [Ar] 3d^6. It has 4 unpaired electrons.

C. Ti^+2 (Titanium ion with a +2 charge):
The electron configuration of Ti^+2 is [Ar] 3d^2. It has 2 unpaired electrons.

D. Cr^+2 (Chromium ion with a +2 charge):
The electron configuration of Cr^+2 is [Ar] 3d^4. It has 4 unpaired electrons.

Now, let's compare the number of unpaired electrons:

A. Mn^+2: 5 unpaired electrons
B. Fe^+2: 4 unpaired electrons
C. Ti^+2: 2 unpaired electrons
D. Cr^+2: 4 unpaired electrons

Among the given options, option A (Mn^+2) has the maximum number of unpaired electrons (5), and therefore, it has the maximum magnetic moment. So, the correct answer is A. Mn^+2.