Final answer:
Beryllium does not typically attain a full octet through sharing of electrons, so chlorine doesn't share its lone pair of electrons with beryllium in BeCl2.
Step-by-step explanation:
The reason chlorine doesn't share its lone pair of electrons with beryllium in BeCl2 is because beryllium does not typically attain a full octet through sharing of electrons. Beryllium only has two valence electrons, so it forms molecular compounds rather than ionic bonds. In BeCl2, the Lewis structure shows that beryllium has four electrons around it, while each chlorine atom has one lone pair of electrons and one shared pair of electrons.