Question

The halide of third group element that is expected to be ionic is:
A. $B{F_3}$
B. $BC{l_3}$
C. $Al{F_3}$
D. $AlB{r_3}$

Answer 1

To answer this question the periodic properties of the elements from the different groups should be known. The periodic properties have opposite trends between left to right and top to bottom. The elements in periodic tables are arranged in a way that every element of each group shows similar physical characteristics and chemical characteristics.

Complete step by step answer:
Boron and aluminum are from group 3 of the periodic table. In the case of ionic compound Ionic bond involves complete transfer of electrons as there occurs the formation of ions called cation and anion, therefore, there exists a huge electrostatic force of attraction which makes it a strong bond. For example, sodium chloride is formed by an ionic bond between sodium and chloride ions.
On the other hand, in the case of a covalent compound Covalent bond involves the sharing of two or more outer shell electrons that can hold all biomolecules together. Shared electrons are difficult to give away because two elements together share the electrons and make the bond stronger. For example, a water molecule has a covalent bond in it.
Now due to the small size of boron, it cannot form an ionic bond by donation of electrons, as the required ionization energy is very high for boron. So, all the compounds of boron are covalent.
On the other hand, in the case of aluminum all the halide is covalent. But in the case of fluoride, due to the strong electronegativity of fluorine, it can make an ionic compound with aluminum.
So, the correct option is C.

Note: Polarization power is the distortion in an ion due to other ion’s power is, which is the phenomena responsible for a covalent character in ionic bonding. This can be explained in detail by considering Farzan’s rules that even a $100\%$ ionic bond has some characteristics of a covalent bond.