Which of the following magnetic properties is never exhibited by liquids and gases under ordinary laboratory conditions?

Introduction / Context:
Materials can respond to magnetic fields in several different ways depending on their atomic and electronic structure. Three commonly discussed magnetic behaviours are diamagnetism, paramagnetism and ferromagnetism. Many solids and some fluids exhibit diamagnetic or paramagnetic responses, and ferromagnetism is seen in familiar materials like iron, cobalt and nickel. This question focuses on which of these behaviours is never observed in liquids and gases under ordinary laboratory conditions, highlighting the special nature of ferromagnetism compared with other magnetic responses.

Given Data / Assumptions:
• We are considering liquids and gases, not solid materials. • The options list diamagnetic, paramagnetic, ferromagnetic and electromagnetic properties. • Ordinary laboratory conditions mean room temperature and pressure without extreme fields. • We use standard definitions of magnetic behaviour.

Concept / Approach:
Diamagnetism is a universal but usually weak property of all materials, including liquids and gases, arising from induced currents that oppose applied magnetic fields. Paramagnetism occurs when materials contain unpaired electrons whose magnetic moments tend to align weakly with an external field; many ionic solutions and gases of paramagnetic molecules show this behaviour. Ferromagnetism, however, requires strong cooperative alignment of atomic magnetic moments in domains and is associated with long range ordering in crystalline solids. This kind of domain structure is not supported in normal liquids and gases because the thermal motion and lack of fixed lattice positions prevent stable domain formation. Therefore, liquids and gases can and do exhibit diamagnetic and paramagnetic behaviour, but they do not show ferromagnetism under usual conditions.

Step-by-Step Solution:
Step 1: Recall that diamagnetism arises from induced currents that weakly oppose an applied field and is present in all materials to some extent, including fluids. Step 2: Recognise that paramagnetism occurs in materials with unpaired electrons and can be observed in some gases and liquid solutions of paramagnetic ions. Step 3: Understand that ferromagnetism involves strong interactions between neighbouring atomic moments leading to spontaneous alignment in domains, which requires a solid crystalline lattice. Step 4: Note that in liquids and gases, atoms and molecules move freely, and the structural stability needed for ferromagnetic domain formation is absent. Step 5: Conclude that ferromagnetic order cannot be maintained in liquids and gases under ordinary conditions. Step 6: Choose ferromagnetic behaviour as the magnetic property never exhibited by liquids and gases in usual laboratory environments.

Verification / Alternative check:
Experimental evidence supports this reasoning. Susceptibility measurements show that many gases, such as oxygen, exhibit paramagnetism, while others like nitrogen show diamagnetism. A number of liquid solutions display dia or paramagnetic responses depending on their solute ions. However, ferromagnetism is observed in solid phases like iron, cobalt, nickel and certain alloys, which have well defined crystal structures. When such solids are melted into liquids, their ferromagnetic ordering disappears, and they behave as paramagnets or diamagnets depending on temperature. High temperature destroys ferromagnetic order even in solids, showing how sensitive it is to structural order and thermal agitation. These facts confirm that ferromagnetism is not present in fluids under ordinary conditions.

Why Other Options Are Wrong:
Option A, diamagnetic behaviour, can occur in liquids and gases because all materials exhibit diamagnetism to some degree. Option B, paramagnetic behaviour, is also exhibited by certain gases like oxygen and by many solutions of paramagnetic salts. Option D, electromagnetic behaviour, is a vague term but generally refers to interaction with electric and magnetic fields, which liquids and gases certainly can have, for example in plasmas or conducting fluids. The only specified behaviour that truly cannot occur in ordinary fluid phases is ferromagnetism, which requires solid like order.

Common Pitfalls:
Students sometimes think that because ferromagnetism is the most familiar form of magnetism, it must occur in any material with unpaired electrons, including liquids and gases. They may not appreciate how crucial fixed lattice positions and exchange interactions are for sustaining ferromagnetic domains. Another pitfall is to overlook the subtle but measurable dia and paramagnetic responses in fluids because these effects are weaker and less obvious than solid ferromagnetism. Remembering that ferromagnetism is tied to solid crystal structure helps you quickly eliminate it as a property of liquids and gases in normal conditions.

Final Answer:
The correct choice is Ferromagnetic behaviour, because liquids and gases can show diamagnetic or paramagnetic responses but do not exhibit ferromagnetism under ordinary laboratory conditions due to the lack of stable domain structures and strong long range ordering.