Maximum Paramagnetisim shown by the following tripositive ion is :

Concept: 

Magnetic Behaviour of f-block elements

• La³⁺ and Lu³⁺ do not contain any unpaired electrons, hence they do not show paramagnetism. All the other tripositive ions of lanthanides (f-block elements) are paramagnetic. 
• Magnetic moments of Ln³⁺ (tripositive ions of lanthanides) ions are generally well described from Russell - Saunders coupling.
• Magnetic moments can be calculated by Lande's formula

Where

g = Lande's splitting factor.

J = Total angular momentum.

L = Total orbital angular momentum.

S = Total spin angular momentum.

J = L + S ( for more than half-filled orbitals).

J = L - S ( for orbitals less than half-filled).

Explanation:

Since La3+ and Lu3+ do not contain any unpaired electrons, they do not show paramagnetism.

• In the case of Nd⁺³

The electronic configuration of Nd⁺³ is given by [Xe]4f³ 

Here, L = 6

S = 

Orbitals are less than half-filled hence J = L - S

J = 

Using the values for L, S and J in the formula for g, we get 

g = 

So, the Magnetic Moment of Nd⁺³ is 

• For Ce⁺³

The electronic configuration of Ce⁺³ is given by [Xe]4f1 

Here, L = 3

S = 

Orbitals are less than half-filled hence J = L - S

Using the values for L,S and J in the formula for g, we get 

g =  

So, the Magnetic Moment of Ce⁺³ is 

So, Among the given tripositive ions Nd⁺³ show maximum paramagnetism.