Question

Which of the following compounds is metallic and ferromagnetic?
A.$Cr{O_2}$
B.$V{O_2}$
C.$Mn{O_2}$
D.$Ti{O_2}$

Answer 1

Hint: We have to remember that due to the arrangements of atoms and its electrons there is a force of attraction or repulsion of a magnetic material called magnetism. Even in the absence of an external magnetic field, ferromagnetic materials exhibit a spontaneous net magnetization at the atomic level. Ferromagnetism is the strongest type in the various kinds of magnetism.

Complete answer:
We must know that when the substances are placed in the magnetic fields (which they are placed in are magnetic materials) that they can alter the magnetic value. Ferromagnetic materials will retain their magnetization even after the external magnetic field is removed, retained for some time. Iron was the first metal to attract magnetic field properties, so ferromagnetism got its name.
A compound containing one or more metal elements bonded to another element, is referred to as a metallic compound. In a metallic compound, metals act as a cation and nonmetals act as an anion.
In solid state, the metal ions of ferromagnetic substances are grouped together into small regions (in solid state) known as domains. The domains act as a tiny target. The domains of the compound get oriented in the direction of the magnetic field producing a strong magnetic effect when placed in a magnetic field.
Among the compounds $Cr{O_2}$ , $V{O_2}$ , $Mn{O_2}$ and $Ti{O_2}$, the compound $Cr{O_2}$ , $Cr$ has $ + 4$ oxidation state. No free spin after getting paired electrons.
And hence Option A is the correct answer.

Note:
We also need to remember that iron, Cobalt, nickel and few other rare-earth metals and alloys contain ferromagnetism. $Cr{O_2}$ is a black synthetic element and used in magnetic tape emulsion as some years ago. In industry there are wide applications of ferromagnetic materials, in generators, an electric motor, generators, transformers and telephones, magnetic strips in the bank cards are widely used by ferromagnetism.