CHEMISTRY COMMUNITY

The linear example given in lecture uses BeCl2. I was wondering in the lewis structure why doesn't Be have lone pair electrons?

Be contributes 2 electrons and each chlorine contributes 7 electrons for a total of 16 electrons. Each chlorine has 3 lone pairs and there are 2 bonds, which account for all the electrons. Be, since it is in Group 2 and period 2, is an exception to the octet rule since it only needs a complete 2s subshell. Thus the 4 electrons from the bonds are sufficient and it does not have any lone pairs.

Be is an exception to the octet rule; it only needs has 2 valence electrons. Since Be bonds with Cl on both sides, it already has 2 valence electrons, so there is no need for additional lone pairs on the Be. BeCl2 is AX2 and linear.

When you add up the total valence electrons of BeCl2 you will see you only have 16 valence electrons and they fulfill Cl octet rule along with getting their formal charge to 0. Be's formal charge is also 0, thus making it a stable molecule with no extra electrons to add as lone pairs.

Be doesn't have lone pair electrons because it is an exception to the octet rule so it cannot take anymore valence electrons. Plus Cl-Be-Cl with three lone pairs around each Cl is already balanced.