Fluorine has nine protons and nine electrons so it is neutral
Answer: Rotation occurs at single bonds that are sigma bonds. Rotational barrier is the amount of activation energy required to covert rotamer to another by rotation that occurs around the sigma bond(C-C single bond). Due to the presence of steric hindrance that is the nonbonding interaction effects the reactivity of ions and molecules, activation energy increases. So the rotational barrier in butenyl cation is high.
Lithium is in the first column of the periodic table and thus can only form one bond with another atom (its ion is Li+)
Oxygen can form two bonds (as in the dioxygen O2).
Hence if you conbine Li and O it has to be Li2O.
