We can answer these questions by considering the periodic table and keeping in mind that the positive nuclear charge of the elements increases from left to right. Thus, the elements on the left of the periodic table are often called electropositive, electron donating, or “electron pushing,” because their electrons are held by the nucleus less tightly than are those of elements to the right. These elements at the right of the periodic table are described as electronegative, electron accepting, or “electron pulling.” Table 1-2 lists the relative electronegativities of some elements. On this scale, fl uorine, the most electronegative of them all, is assigned the value 4.

http://webcache.googleusercontent.com/search?q=cache:E6ZCL75...

The Electron-Pushing Formalism Using Curved Arrows
www.science.oregonstate.edu/.../elec_push.htm
Oversett denne siden
In organic chemistry, we use a formalism called "electron pushing" to describe bond ... The head of the arrow points to where the eletron(s) wind up. If we make a ...

--------------------------------------------------
Note added at 23 mins (2015-11-29 17:57:37 GMT)
--------------------------------------------------

Arrow pushing or electron pushing is a technique used to describe the progression of organic chemistry reaction mechanisms.[1] It was first developed by Sir Robert Robinson.[2] In using arrow pushing, "curved arrows" or "curly arrows" are superimposed over the structural formulae of reactants in a chemical equation to show the reaction mechanism. The arrows illustrate the movement of electrons as bonds between atoms are broken and formed. Arrow pushing is also used to describe how positive and negative charges are distributed around organic molecules through resonance. It is important to always remember, however, that arrow pushing is a formalism and electrons (or rather, electron density) do not move around so neatly and discretely in reality.