Which is the central atom in Lewis Dot Structures?
The video is wrong if it says "the central atom ... is always the least electronegative atom".  

There are chlorine oxides with Cl central such as perchlorate, chlorate and $\ce{ClO2}$, even though $\ce{Cl2O}$ has O central. 

There are $\ce{SeCSe}$, $\ce{CAt4}$, $\ce{NI3}$ and $\ce{Li6C}$ each with the more electronegative element central.