What is the electronegativity of carbon

Chemistry Lexicon / Electronegativity and Polarity

Before we deal with the subject of electronegativity, we have to look back one more time, to the subject of "atomic bonding". Atoms hold together in atomic bonds because the atomic nuclei use electron pairs and these are attracted by both atomic nuclei. As a result, the atoms reach the noble gas state, which is the goal of almost all reactions.

However, the attraction of the binding electrons depends on the protons in the nucleus, so it is clear that the number of protons determines how strong the attraction of the binding electrons is. Three simple examples:

In the case of a bond between two carbon atoms, it is two identical atomic nuclei that pull on the shared binding electrons. The binding electrons are exactly in the middle here.

In the bond between a hydrogen and a carbon atom, the attraction to the bonding electrons differs. Because the carbon atom has more protons in its core. Therefore the attraction by the carbon atom is stronger. However, the binding electrons are a little further away from the core of the carbon atom because the binding electrons are on the second shell. This in turn reduces the attraction somewhat.

With this bond between a hydrogen and an oxygen atom, the difference is even greater than before with hydrogen compared to carbon. It is therefore to be expected that the binding electrons between hydrogen and oxygen atoms will be more attracted to the oxygen. Carbon and oxygen atoms have the same number of shells, but oxygen has more protons in the core.

How can one understand that the electrons are more attracted to the oxygen atom than to the hydrogen atom? It is not that easy, because you have to remember that the electrons are not - as can be seen in the picture - in a fixed place. They have to be in motion, otherwise they would be drawn to the atomic nucleus. The "position" of an electron can be thought of as a probability of its location.

The video shows a simulation that uses the light blue area to show the probability of the electrons being located. The contour lines (which look like contour lines on a map) show the areas with equal probability.

At the beginning of the simulation, the atoms are not yet connected to each other. After the start, the bond is formed and the blue area is concentrated between the two atomic nuclei (the crosses at A and B).

The change in the attraction by the slide control causes the cloud to be shifted and thus the probability of the electrons being located. The greater the difference in attraction, the greater the likelihood that the electrons will be at the atom with the stronger attraction.

The following simulation, which you can also operate yourself, shows moving electrons if you use the setting "Electron distribution view" select. In addition, the red "cloud" is changed if you have selected different atoms. Even if the electrons move too fast to be able to follow them exactly, one recognizes that - depending on the atom selected - they are more or less near one or the other atom.

The binding electrons, which are more or less attracted to one of the atoms, are indicated in the Lewis notation by drawing a wedge instead of a line for the binding electrons.

Electronegativity

So far we have only mentioned that different atoms attract the binding electrons to different degrees. This attraction depends on two factors:

  1. How many protons does the atomic nucleus have? (the more the stronger the attraction)
  2. How big is the atom, so how many shells does it have? (because the closer to the core the stronger the attraction)

With the help of the information in the periodic table, one can say exactly how many protons the atomic nucleus has and how many shells, but it is not so easy to estimate how strong this has in each case. The diagram with the atomic radii also shows that the atomic radius changes within a period, as the greater number of protons attracts the electrons more strongly.

Fortunately, this assessment was made for us and quantified in the form of a number that indicates exactly how strong the attraction to the binding electrons is.