Which of the following statements is/are correct regarding ionic compounds?

Ionic Bond:
In the periodic table, the highly electronegative halogens and the highly electropositive alkali metals are separated by the noble gases. The formation of a negative ion from a halogen atom and a positive ion from an alkali metal atom is associated with the gain and loss of an electron by the respective atoms. The negative and positive ions thus formed attain stable noble gas electronic configurations. The noble gases (with the exception of helium which has a duplet of electrons) have a particularly stable outer shell configuration of eight (octet) electrons, $n s^{2} n p^{6}$. The negative and positive ions are stabilised by electrostatic attraction.
Covalent Bond:
Langmuir (1919) refined the Lewis postulations by rejecting the idea of the stationary cubical arrangement of the octet and by introducing the term covalent bond. The Lewis-Langmuir theory suggests that when both the atoms taking part in a chemical combination are short of electrons than the nearest noble gas configuration, they can share the electrons in order to complete their octets. Each atom contributes the same number of electrons to form common pairs which are then shared by both atoms.

Which is an electron deficient compound?

Explain why?

${\mathrm{BeCl}}_2$ shows a high degree of covalence in its reactions, whereas ${\mathrm{BaCl}}_2$ is predominantly ionic.